Monday, 28 January 2008

MMIC PBL - part 2 (avian flu)

Avian Influenza (Bird Flu):

Introduction:


Influenza viruses are segmented, negative-sense, single-stranded RNA viruses of the family Orthomyxoviridae and are divided into A, B and C.

Avian Influenza or bird flu refers to the different strains of influenza virus adapted to birds, a specific host. This is known as Influenza A virus, whereby all subtypes are adapted to birds. Generally, most avian influenza viruses are noninfectious for most species of birds, and are usually asymptomatic (no symptoms) if infectious. Hence, they do not pose much of a threat despite being highly transmissible.

However, domestication of birds/poultry has produced subtypes of avian species that are vulnerable to the viruses that rapidly mutate, causing many bird-related deaths. These become dangerous when the virus mutates and is transmissible to humans, such as the H5N1 virus. Other such viruses includes the H1N1 (Spanish flu) and the H9N2 (Hong Kong flu). Alternatively, viruses may mutate and infect an intermediate host such as the pig/swine, which support reassortment of genes that create new subtypes, before going on to infect humans.

As of 2004, Indonesia has had outbreaks of the H5N1 virus – avian flu. This strain is deadly to humans and usually spread through contact with poultry and domesticated birds like the fighting cock in Thailand. Indonesia has had outbreaks of H5N1 viruses, mainly from the poultry breeding farms. Typically, H5N1 transmission is restricted to from bird to humans. However in 2006, there was a case of human to human transmission of H5N1 versus between a group of small families, but the spread appears to have died off. H5N1 can last indefinitely at a temperature dozens of degrees below freezing.

Hence, this blog will concentrate on H5N1 virus as it is the most relevant in indonesian context as well as given time, and threatening to human life.

Strains of Influenza A:
Subtypes of influenza A as previously mentioned are based on antigenic relationships of the hemagglutinin (H) and neuraminidase (N) surface glycoproteins, two proteins on the surface of the virus that allow it to enter and exit host cells.
o Each virus has one HA and one NA protein, potentially in any combination
o Sixteen different hemagglutinins (H1-H16) and nine different neuraminidases (N1-9) have been identified to date.
o Typically, most avian flu is restricted to bird to bird transmission. The most deadly being H5N1 strain as it can spread from bird to human.


commons.wikimedia.org > wiki > Flu_und_legende_color_c.jpg

Virulence:

Virulence is determined based on antigenic properties of the strain.
Highly pathogenic avian influenza (HPAI) viruses causes systemic disease with rapid death rate, mostly of the H5 or H7 subtypes
Low pathogenic avian influenza (LPAI) viruses cause a localized infection with little or no disease.
Virulence factor is also correlated with the hemagglutinin cleavage site – all HPAI have multiple basic amino acids (arginine and lysine) at the HA0 cleavage site, while LPAI have 1 or 2 amino acids. Multiple amino acid sites allow for a wider range of protease cleavage, resulting in higher amounts of reassortment, increasing virulence and susceptibility in other animals. This also allows for host protease to act on HPAI, causing it to replicate systemically, damaging vital organs and tissues, which results in severe disease and death as seen in H5N1.

Pathogenicity:
Spread to humans via contact, potentially airborne (incubation period is longer, less adapted to droplet transmission):
- Directly from birds or from avian virus-contaminated environments to people (consumption of poultry products, direct contact with live poultry – bodily fluids such as blood, salvia etc and contaminated food sources).
- Through an intermediate host, such as a pig.
Typically develops 1 to 5 days following exposure.

- H5N1 virus particles enter blood stream through contact with chickens/ poultry. Virus attaches to cell surface sialic acid via receptor site on the haemagglutin (HA) site. Adhere to endothelium in respiratory tract.
- Internalised by receptor mediated endocytosis within cellular endosomes
- Viral envelope and cell membrane fuses, releases viral particles into cytosol.
- Cytosol acidic pH causes conformational changes in HA structure to form HA2, that binds to membrane to open M2 ion channel.
- Ions from endosome enters virus particle, triggering another set of conformational changes to HA, releasing viral nucleocapsids into the cell cytoplasm.
- Viral transcription occurs in the nucleus by viral encoded polymerase, consisting of a complex of 3 P proteins. This is activated by RNA polymerase II that caps and methylates the 5’ terminal.
- Viral proteins such as NS and NP are synthesized
- NS proteins interact with M proteins for nuclear export of viral RNPs.
- Templates for viral synthesis remain coated in nucleocapsid which are neither trunucated or methylated
- Viral mRNA are synthesized by viral encoded polymerase using positive template strand.
- Individual viral components arrive at budding sites by different routes
- Nucleocapsid is assembled in the nucleus and moves out to cell surface
- Glycoproteins HA and Na are synthesized in the endoplasmic reticulum, modified and inserted into the plasma membrane
- M protein serves as a bridge, linking nucleocapsid to sytoplasmic ends of glycoproteins
- Progeny virons bud off from cell when HA is cleaved to HA1 and HA2 by proteolytic enzyme from host. NA removes terminal sialic acid from cellular and viral surface viral proteins, facilitating release of viral particles from cell.

Signs and symptoms:
Common:
- Cough
- High fever (typically > 38°C)
- Headaches
- myalgia (muscle ache/pain)
- malaise (general discomfort)
- Sore throat
- Shortness of breath
- Diarrhoea
- A relatively mild eye infection (conjunctivitis), sometimes the only indication of the disease.

Severe signs and symptoms:
- Viral pneumonia
- Acute respiratory distress (the most common cause of bird flu-related deaths)
- Seizures

Laboratory Diagnosis:

Samples to be taken: Nasal washings, gargles, throat swabs. Within 3 days of onset of symptoms.
Sample conditions: Held at 4oC until inoculation into cell culture (freezing/thawing reduces viral recovery).

Isolation methods: embryonated eggs, monkey kidney cells.

1) Viral isolation
Viral isolates can be identified by hemagglutination inhibition, that rapidly determines influenza type and subtype. Test serum/culture fluid with hemagglutination inhibitor to check for presence. If results are negative, make a passage into fresh culture as influenza is typically fastidious and grows slowly.

2) Fluorescent antibodies
For rapid diagnosis, cell cultures on coverslips may be inoculated and stained 1 or 2 days with monoclonal antibodies to respiratory agents. Positive confirmed with use of single fluorescent antibody.
Alternatively, a more rapid diagnosis with less sensitivity is directly using fluorescent antibody on nasal aspirate.

Sample: Blood, serum.

3) Serology
Normal individuals will produce influenza antibodies during infection, such as antibodies to hemagglutinin, neuraminidase, nucleoprotein and matrix. These can be deteced by ELISA or hemagglutination inhibition (HI). These are performed using the patient’s serum extracted from blood stream. ELISA is more sensitive than other assays, while HI enables pin pointing of influenza strain. However, this method is dependant on patient’s antibody response system.

Necessary precautions:
1) Avoid contact with live birds, and all forms of poultry:
- Chickens, ducks, turkeys and geese and their feces, feathers and pens if at all possible.
2) Avoid poultry products in Indonesia, as cases of H5N1 have been reported there.
3) All foods from poultry, including eggs should be cooked thoroughly. Egg yolks should not be runny or liquid. Influenza viruses are destroyed by heat, hence cooking temperature for poultry meat should be 74oC (165 F).
4) Avoid cross contamination of other foods by use of separate kitchen utensils and surfaces exposed to raw poultry.
5) Wash hands with soap and water after any poultry contact.
6) Avoid live food markets.

Treatment:
Antivirals:
Suppress virus, keep it from replicating and infecting within the host. Must be taken soon (often within 48 hours following infection).
Neuraminidase inhibitor:
Mode of action consists of blocking the function of the viral neuraminidase protein, preventing the virus from reproducing.
1. Relenza
2. Tamiflu

Vaccination:
Vaccines expose an individual to a weakened/dead virus to stimulate antibody production against it, so that immune system can fight off infections should it arise.
There are at least 15 different strains of avian flu and they are constantly mutating, hence vaccination may not prove to be effective for long.
Live vaccines (attenuated, weakened):
- Requires less antigen (active ingredient) than killed vaccine.
Live vaccine may contain too few copies of the weakened virus to trigger an immediate immune response.
However, once inside the host, the virus can replicate to render it detectable by the immune system and trigger an immune response.
Does not require injection – oral consumption will do.
Killed virus (inactivated):
Must be injected – only route to administer them that will bring them into contact with the immune system.
Requires larger dosage than live vaccines due to its lack of ability to multiply within host.
3. Recombinant vaccine:
Genetically engineered vector (usually a low virulence virus) to express H5N1 protein antigen on surface, to stimulate immune response (production of antibodies).


References:
sciencedaily.com > releases > 2007 > 08/070828154944.htm
cidrap.umn.edu > cidrap > content > influenza > avianflu > news > dec3005halvorson.html
evolution > berkeley.edu > evolibrary > news > 51115_birdflu
http://www.cbc.ca/> news > background > avianflu > protection.html
http://www.cdc.gov/ > ncidod > EID > vol10no4/03-0396.htm
Cheers,
Debra, TG02

Sunday, 27 January 2008

Protozoa pathogens – post 2 (Eunice)

Plasmodium species [1]

(Picture taken from http://en.wikipedia.org> malaria parasite> plasmodium falciparum)

Characteristics: In P. falciparum, only early trophozoites and gametocytes are seen in the peripheral blood. The parasitised RBCs are not enlarged and it is common to see multiple infected RBCs.


Toxoplasma species [2]

(Picture taken from http://en.wikipedia.org> toxoplasma)

Characteristics: Tachyzoites are the motile, asexually reproducing form of the parasite.


Helminths – Wuchereria bancrofti [3]
(Picture taken from http://en.wikipedia.org> helminths> wuchereria bancrofti)

Characteristics: The microfilaria is sheathed and the tail is tapered to a point. The nuclear column loosely packed, the cells can be visualized individually and do not extend to the tip of the tail.


Leishmania species [4]

(Picture taken from http://google.com> images> leishmania)

Characteristics: Leishmania cells have two morphological forms: promastigote (with an anterior flagellum) in the insect host, and amastigote (without flagella) in the vertebrate host.

Gardia, Cryptosporidium and Cyclospora [5]
Image of Gardia:
(Picture taken from http://en.wikipedia.org> gardia)

Image of Cryptosporidium
(Picture taken from http://en.wikipedia.org> cryptosporidium)

Image of Cyclospora
(Picture taken from http://en.wikipedia.org> Cyclospora)

REFERENCES
1) http://en.wikipedia.org> malaria parasite
2) http://en.wikipedia.org> toxoplasmosis
3) http://en.wikipedia.org> helminths> wuchereria bancrofti
4) http://en.wikipedia.org> leishmania
5) Foodborne pathogens: hazard, risk analysis and control / edited by Clive de W. Blackburn and Peter J. McClure

PBL blog 2 - Viruses part 2

In this post, I will be concentrating on 5 main viruses as a follow up on the previous post.

1. Chikungunya


Caused by:
Alphavirus of the Togaviridae family. (1)

Transmission: Ades aegypti mosquito vectors (1)

Pathogenesis: Sylvatic cycle.


Chikungunya virus under scaning electron microscope. Picture taken from: http://www.flickr.com/photos/ajc1/1257163357/

Symptoms: Petechial (small red dot) or maculopapular (bumpy bumps) rash around the limbs and trunk. Polyarthritis resulting in debilitating pain causing contortions in affected joints, headache, slight photophobia (sensitivity to light), fatigue, nausea, vomiting and muscle ache. There are many other symptoms depending on age and severity of the disease. Note that the disease is similar to dengue. (2)







Women suffering from severe joint pains in a hunched position. Picture taken
from : http://www.semp.us>
publications>biot_reader.php?BiotID=339



Suitable precaution:
Avoid mosquito bites such as wearing long sleeves and long pants to cover the limbs and to treat clothes with permethrin or alternatively, use insect repellents.


2. SARS (Severe Acute Respiratory Syndrome)

Caused by: SARS coronavirus



<---- Sars coronovirus under scanning electron microscope. Picture taken from: http://pathmicro.med.sc.edu/graduate/corona-cdc.jpg


Transmission: Spread mainly by close person-to-person contact. When an infected person coughs or sneezes, droplets of mucus or saliva that contain the virus are sent through the air. Once these droplets land on the mouth, nose or eyes, an infection can occour.
Kissing, touching, sharing utensils for eating and drinking, or talking with an infected person is also a risk factor for infections. if you travel to countries with SARS. There is no treatment for SARS. Scientists are testing treatments and vaccines. (8)


Pathogenesis:

Week 1: Fever, muscle aches and other symptoms that generally improves after a few days.

Week 2: Patients experiences recurrance of fever, diarrhea and oxygen desaturation (characterised by breathing difficulties) and severe worsening of condition of the patient may occur. (6)


Damage of alveolar (lung) tissue due to SARs infection. Picture taken from http://pathmicro.med.sc.edu/virol/coronaviruses.htm


Week 3: Patients requires ventilatory support and some may develop end-organ damage and severe lymphopenia (abnormally low levels of lymphocytes, which is a type of white blood cells) resulting in death.

Symptoms: Patients are present with a high fever of > 38.0°C, including chills, headache, dizziness, rigors (shaking due to high fever), malaise (general feeling of discomfort), muscle aches.

Suitable precaution: Observe hygiene such as frequent washing of hands and avoid sharing of utensils.



Caring for a SARs patient in the ICU. Notice the attire of the clinicians and the pathogenecity of the virus. Picture taken from: http://www.bact.wisc.edu/themicrobialworld/SARS.html


3.Tick borne encephalitis

Caused by: Tick-borne encephalitis virus (TBEV) which is a member of the Flaviviridae family.

Transmission: Tick bites of the ixodes species

Pathogenesis: Ticks are the hosts and the reservoir of the virus. TBEV chronically infects ticks and is transmitted from larva to nymph to adult ticks. TBEV infects humans when tick bites during the peak period of april to november. (9)




Tick responsible for TBE. Picture taken from: http://www.hqusareur.army.mil/htmlinks/Press_Releases/2007/May2007/08May2007-01.htm


Symptoms: Asymptomatic for the first 2 weeks. Non-specific symptoms including fever, muscle aches, anorexia, headache, nausea and vomitting.


Suitable precaution: Vaccination and using insect repellents and protective clothing such as long sleeves, long pants and covered shoes.


4. Influenza (Flu)

Caused by: Family of Orthomyxoviridae viruses known as the influenza viruses.

Transmission: From infected bird droppings, coughing and sneezing of infected person, creating aerosols of the virus and contact with contaminated surfaces. (5)


<--- Model of the influenza virus. Picture taken from: http://www.3dscience.com/Resources/Influenza_Virus.php


Pathogenesis: Entry to host cells followed by binding of the host's columnar epithelial cells at the respiratory tract. Fusion with the cell's membrane and release of viral RNA which replicates within the nucleus, synthesizing structural and envelope proteins then releasing virions infecting neighbouring cells.

Symptoms: Fever, extreme coldness, sore throat, muscle pains, severe headache, coughing, weakness, fatigue, nasal conjestion, redden irritated watery eyes, coughing, sneezing and general discomfort.

Suitable precaution: Influenza vaccinations and observe hygiene.


5. Hepatitis A

Caused by: Hepatovirus hepatitis virus (HAV) (3)

Transmission: Contaminated food and water.

Symptoms: Nausea, diarrhea, fever, jaundice, fatigue, abdominal pain, loss of appetite and weight loss. (4)

Hepatitis virus under the scanning electron microscope. Picture taken from: http://zh.wikipedia.org/wiki/%E7%94%B2%E5%9E%8B%E8%82%9D%E7%82%8E

Suitable precaution: Vaccination and throughly cook food, drink boiled water and observe personal hygiene.



References:

1. Chikungunya: http://en.wikipedia.org/wiki>Chikungunya

2.
 Chikungunya Fever Fact Sheet :
http://www.cdc.gov>ncidod>dvbid>Chikungunya>chikvfact.htm

3. Hepatitis A: http://www.cdc.gov>ncidod>diseases>hepatitis>a>fact.htm

4. Hepatitis A:
http://en.wikipedia.org/wiki>Hepatitis_A

5.
Influenza: http://en.wikipedia.org/wiki>Influenza

6. SARs: http://www.sarsreference.com>sarsref>diag.htm

7. SARs: http://www.sarsreference.com>sarsref>prevent.htm

8.
SARs: http://www.sarsreference.com>sarsref>trans.htm

9.Tick bourne encephalitis:
http://www.cdc.gov>ncidod>dvrd>spb>mnpages>dispages>TBE.htm



Yeng Ting
TG02

Water borne protozoa_elaine(2nd blogging)

Protozoa: single-celled parasites
--> they are unicellular eukaryotes, meaning that they are charactistics organelles. They are relatively large and some are visible with the naked eye. They occupy a vast array of habitats and niches and have organelles similiar to those found in other eukaryotes cells as well as specialized organelles. Protozoa usually reproduce asexually by binary fission. (3)


Infection with parasites is a major cause of morbidity and mortality in tropical and semitropical countries
http://www.dpd.cdc.gov/dpdx/HTML/Cyclosporiasis.htm
Transmission:
-->faecal-oral
-->arthropod vectors
-->intermediate hosts e.g. fishes or snail
Prevention:
-->Treat drinking water with high efficiency filtration and/or chemical disinfection such as chlorination or ozonation (4)

1) Giardia Lamblia (giardiasis):
--> A flagellated protozoon and an important cause of diarrhea worldwide. (1)
--> is a flagellated protozoan parasite that colonises and reproduces in the small intestine, causing giardiasis.
--> Giardiasis does not disseminate haematogenously, nor does it spread to other parts of the gastro-intestinal tract, but remains confined to the lumen of the small intestine. Giardia trophozoites absorb their nutrients from the lumen of the small intestine, and are anaerobes.
http://www.brown.edu/Courses/Bio_160/Projects2004/rotavirus/Epidemiology.htm
[Route of infection]: Faecal-oral

[Pathogenesis]: cysts of Giardia Lamblia have been demonstrated in the drinking water. Ingestion of cysts—the resistance, infective stage—is followed by the production of trophozoites in the upper small intestine. Trophozoites cause irritation, which leads to gastrointestinal symptoms.

[Clinical features]
Symptoms: diarrhea, mild to severe, with characteristic light-coloured fatty tools; abdominal pain: cramps, with flatulence and epigastric tenderness; anorexia
Malabsorption: steatorrhoea is not common and may lead to the full-blown malabsorption syndrome.

2) Cryptosporidium Parvum (Cryptosporidiosis): (1)
-->Cryptosporidium is a protozoan pathogen of the Phylum Apicomplexa and causes a diarrheal illness called cryptosporidiosis.
-->Human infection is often acquired as a result of animal slurry contaminating water supplies.
http://www.cbu.edu/~seisen/CadSu0402.htm
[Transmission]:
The infective stage is the oocyst, passed in faeces: transmitted person-to-person, animal-to-person or via contaminated water.

[Clinical features]
Symptoms: self-limiting diarrhea in the immunocompetent individual.


3) Isospora Belli:
--> humans seem to be the only host of this parasite, which infects the small intestine. (2)
http://www.tropeduweb.ch/factsheets/fs_parasital_class_protozoa.html
[Transmission]
Faecal-contaminated food and water

[Clinical Features]
In the immunocompetent infection is often asmptomatic and the diarrhea, when present, tends to be mild.
[Pathogenesis]
In the immunocompetent, infection is generally asymptomatic or a self-limiting gastro-enteritis. However, in chronic infections, severe diarrhoea and fat malabsorption can occur.
Infection in immunocompromised individuals ranges from a self-limiting enteritis to severe diarrhoeal illness resembling that of cryptosporidiosis.

4) Cyclospora Cayetanensis (Cyclosposiasis): infect the small intestines (1)
http://www.tmd.ac.jp/med/mzoo/parasites/General/cyclospora.gif
[Transmission]
The infective stage is the oocyst passed in faeces (waterborne)

[Clinical features]
Symptoms: diarrhea, remitting and relapsing, sometimes lasting as long as 6 weeks; malabsorption in some cases; weight loss


5) Entamoeba Histolytica (amoebiasis): a common infection in tropical countries such as Indonesia where the sanitation is poor. (2)
http://parasite.tmu.edu.tw/lab-pict/Protozoa/page/image6.html
[Route of infection]
Faecal-oral, owing to contaminated water

[Clinical features]
Diarrhea, progressing rapidly to bloody diarrhea accompanied by fever and painful abdominal cramps, symptoms may pesist into a chronic relapsing state. Sometimes progresses to dilatation of the colon, with the risk of intestinal perforation.

[Complication]
Amoebic absecess owning to spread to the liver causing painful enlargement and accompanied by high fever, raised white cell count and high ESR.


ReferencesBook:

(1) Medical microbiology 4th edition. written by patrick R. Murray, Ken S. Rosenthal, George S. Kobayashi, Micheal A. Pfaller

(2)Book: microbiology of waterborne disease. written by S L Percival, R M Chalmers

(5) Carlo Denegri Foundation. Intestinal parasites. html>iso1.htm/">http://www.cdfound.to.it>hTML>iso1.htm

Saturday, 26 January 2008

PEI SHAN - Fungal pathogens 2nd post

Most possible fungal agents that might be encountered by the soldiers - Beware!!!

1. Dermatophytes
-Epidermophyton


Epidermophyton floccosum
Image from: http://www.mycology.adelaide.edu.au/

-Microsporum

Microsporum fulvum
Image from: http://www.mycology.adelaide.edu.au/

-Trichophyton



Trichophyton concentricum
Image from: http://www.mycology.adelaide.edu.au/



T. mentagrophytes var. interdigitale
Image from: http://www.mycology.adelaide.edu.au/


Trichophyton rubrum downy strain
Image from: http://www.mycology.adelaide.edu.au/

Characteristics: Filamentous fungi invading surface keratinized structures e.g. skin, hair, nails. Hyphae penetrate between cells. (1)

Disease: Tinea (fungal infection), ringowrm, athlete's foot

Transmission: By fungal material on skin scales

Pathogenesis: Skin inflammation, pruritus - sometimes localized hypersensitivity reactions. (1)

Treatment: Topical antifungal agents (griseofulvin)

Prevention: Improved skin care and hygiene


2. Yeasts
Candida Albicans

Candida albicans
Image from: http://www.mycology.adelaide.edu.au/


Characteristics: Dimorphic fungus - occurs as yeast on mucosal surfaces as component of normal flora but forms hyphae when invasive. Produces opportunistic infections in stressed, suppressed and antibiotic0treated individuals. (1)

Disease: Candidiasis, thrush

Transmission: Part of normal flora of skin, mouth and intestine

Pathogenesis: Localised mucocutaneous lesions; invasion of all major organs in disseminated condition (1)

Treatment: Oral and topical antifungals e.g. nystatin, miconazole.


3. Blastomyces Dermatitidis

Image from: http://www.mycology.adelaide.edu.au/

Characteristics: Dimorphic fungus. (4) Invades through lungs, can become widely disseminated in body. (1)

Disease: Blastomycosis

Transmission: Inhalation of airborne spores

Pathogenesis: Fungal infection in lungs. Similar to tuberculosis. (1) Can produce abscesses.

Treatment: Ketoconazole


4. Hyphomycetes
(hyaline moulds)
Aspergillus

Hyaline hyphomycete showing distinctive conidial heads with flask-shaped phialides arranged in whorls on a vesicle. (3)
Image from: http://www.mycology.adelaide.edu.au/

Characteristics: Filamentous fungi causing opportunistic infections in immunocompromised patients. Occur widely in external environment. Invade lungs and blood vessels. (1)

Disease: Aspergillosis

Transmission: Inhalation of airborne stages

Pathogenesis: Causes thrombosis and infarction when blood vessels invaded. Partial blockage of airways from fungal mass. Allergic bronchopulmonary reactions. (1)

Treatment: Amphotericin B


5. Hyphomycetes
(dematiaceous moulds)
Sporothrix Schenckii

Conidiophores and conidia of S. schenckii
Image from: http://www.mycology.adelaide.edu.au/
Characteristics: Dimorphic fungus that occurs in external environment. Invades subcutaneous tissues (1)

Diease: Sporotrichosis

Transmission: Direct fungal contamination of wounds in skin

Pathogenesis: Ulceration or abcess formation in draining lymphatics (1)

Treatment: Potassium iodide, ketoconazole

Prevention: Protection of skin especially covering of wounds
References
1. Book: Medical Microbiology third eition by M., Cedric at. el.
2. Dermatophytes: http://www.cfsph.iastate.edu > Factsheets > pdfs > dermatophytosis.pdf
3. Mycology: http://www.mycology.adelaide.edu.au
4. Blastomyces dermatitidis: http://www.emedicine.com > med > topic231.htm
5. Malassezia furfur: http://www.anaisdedermatologia.org.br > artigo_imprimir_en.php?artigo_id=10192
6. Histoplasma capsulatum: http://wonder.cdc.gov > wonder > prevguid > p0000406 > p0000406.asp
Reported by Pei Shan, Tg02

Possible Viral Diseases that Might Be Contracted in the Jungle (Part 1 Updated)

Cheng Hong: Mmic viral posting2


In the previous blog posting there are 5 viral diseases (part 1) that is listed, in this blog, we will focus on the more common viral disease that might be contracted in the Indonesia jungle. Mainly: Dengue, Rabies, Yellow Fever.


1.Dengue(Winkipedia>Dengue)

-Cause by:
--Dengue virus-Flavivirus family

-Transmission:
--By the bite of the Ades aegypti mosquito
--Bites during the day
--Not transmitted from person to person
-Pathogenesis and symptoms:
--Dengue fever (breakbone fever): Sudden onset of fever, skin rash, muscular pain, recovers in about a week
--Dengue hemorrhagic fever: Acute onset, decrease in platelet count, causing hemorrhage under the skin and GI tract
--Dengue shock syndrome: Severe hypotension(low blood pressure), may cause shock, maybe fatal if not treated immediately

-Suitable precaution and treatment:
--Wear mosquito repellent on exposed skin area and wear long pants and long sleeve shirt when possible.
--Supplementation with intravenous fluids to prevent hypotension
--Platelet transfusion is needed in rare cases if the platelet level drops significantly (below 20,000)



2. Hantavirus Diseases

-Unlikely to happen as, Hantavirus is spread through rodent’s feces, saliva, urine, rodents are unlikely to be found in the jungle of Indonesia and ingesting its feces/urine is also quite unlikely
-But army men should note the hygiene when consuming food



3. Japanese Encephalitis(Winkipedia>Japanese Encephalitis)

-Culex tritaeniorhynchus it is more prevalent in the Northern Asia, parts of Africa thus unlikely to be found in the jungles of Indonesia.
-But army men should take precautions from getting mosquito bites



4. Rabies
-Cause by:
--Rabies virus( rhabdovirus: (-)ssRNA)- Lyssavirus family
-Transmission:
--Bites from infected wild animals (bats, wild boar, monkeys etc)
--Virus present in the saliva

-Pathogenesis and symptoms:
--Infect human when saliva containing rabies virus from animal bite penetrates into skin
-- The virus enters the peripheral nervous system and travels along the nerves towards the central nervous system and reaches the brain to trigger the disease.
--Headache, fever, malaise, numbness on site of bite, hallucinations, spasms, death must occur if not treated immediately

-Suitable precautions and treatment:
--Vaccination(anti-rabies) available, post exposure treatment also available
--Avoid contact with wild animals, if bitten, clean wound and wash with disinfectant immediately
--Army men should not agitate wild animals to prevent them from biting



5. Yellow Fever
(Winkipedia>Yellow Fever)
-Cause by:
--Yellow fever virus (arbovirus: (+)ssRNA)- Flavivirus family
-Transmission:
--Bite from infective Aedes aegypti mosquito
--Normally bite during the day
-- Aedes aegypti mosquito is also prevalent in Southeast Asia thus Yellow Fever might be contracted in the jungles of Indonesia
-Pathogenesis and symptoms:
-- After the bite, the viral particles is deposited through the skin in infected arthropod saliva
--The virus replicates locally, then transported to the rest of the body via the lymphatic system, then to other parts of the body
--Acute onset, fever, muscular pain, headache, chills, nausea, vomiting, bradycardia
--May proceed to development of jaundice, abdominal pain, haemorrhage (50% of which will die)

-Suitable precaution:
--Vaccination available
--Wear mosquito repellent on exposed skin area and wear long pants and long sleeve shirt when possible.
--For serious cases: Fluid replacement, fighting hypotension and transfusion of blood derivates




(top to bottom): Dengue virus, Rabies virus, Yellow fever virus, Ades mosquito
References:
http://www.who.int/mediacentre/factsheets/fs100/en/print.html
http://www.who.int/biologicals/areas/vaccines/yellow_fever/yellow_fever_background/en/print.html http://www.jungleformula.co.uk/jfrange/index.html

Sunday, 20 January 2008

PBL2: Introduction

Recently report shows that there are outbreaks of viral, fungal and protozoa diseases among platoons of army soldiers in Indonesia. Soldiers reported sick after 2 weeks of jungle warfare training. It is of concern to the ministry that there are also sporadic reports of avian flu in the nearby villages. Ministry of environment are also concerned that significant health risks exists in certain areas of Indonesia related to poor public health sanitation efforts in food, water, and infections disease control.

Major threats:

Food or waterborne Disease: Food and waterborne disease are normally caused by fecal contamination (diarrhea, Hepatitis A/E, typhoid fever), which is seem to be the greatest infectious threat to the government.

Vector-Borne Disease: Risk of malaria is variable, occurring year round and country wide. P. palciparum predominates. Dengue Fever and Japanese Encephalitis and malaria are seem to transmit the faster near rural and periurban areas, especially where extensive mosquito-breeding sites and pig-rearing areas coexists.

Respiratory Disease: tuberculosis is highly endemic. Risk is year-round and countrywide. Incidence likely is increasing.

Some requirement and/or schemes are listed below to be followed strictly to ensure that future batches of soldiers stay healthy throughout the jungle warfare training:

Requirement before deployment:
Ensure that routine immunizations for deployable personnel are up to date.
obtain adequate personal protective supplies and complete a pre-deployment health assessment.

Requirements during deployment:
deploy appropriate preventive medicine personnel and equipment
Avoid local food, water. Never eat undercooked ground meat, poultry, raw eggs, and unpasteurized dairy products.
Perform environment hazards assessments as needed.
Avoid contact with animals and hazardous plants
avoid contact with lakes, rivers, streams, and other surface water

Requirement after deployment:
Seek medical care immediately if ill, especially with fever.
Receive preventive medicine debriefing after deployment

In the following blogs described some possible virus, protozoa, and fungal pathogens that might have cause the outbreak of disease. Avian flu is considered to.

PBL 2 - Possible fungal pathogens by PEI SHAN

Common fungal pathogens that the soldiers may encounter in the indonesia jungle are as listed below:

1. Dermatophytes
 Epidermophyton floccosum
 Microsporum sp.
o Microsporum canis
o Microsporum ferrugineum
o Microsporum fulvum
 Trichophyton sp.
o Trichophyton ajelloi
o Trichophyton concentricum
o Trichophyton mentagrophytes var. interdigitale
o Trichophyton mentagrophytes var. mentagrophytes
o Trichophyton rubrum
o Trichophyton rubrum downy strain
o Trichophyton rubrum granular strain
o Trichophyton tonsurans
o Trichophyton verrucosum

2. Yeasts
 Candida
o Candida albicans
o Candida famata
o Candida glabrata
o Candida guilliermondii
o Candida krusei
o Candida lusitaniae
o Candida parapsilosis
o Candida tropicalis
 Cryptococcus
o Cryptococcus gattii
 Malassezia furfur


3. Dimorphic Pathogens
 Blastomyces dermatitidis
 Histoplasma capsulatum

4. Hyphomycetes
(hyaline moulds)

 Aspergillus sp.
o Aspergillus flavus
o Aspergillus fumigatus
o Aspergillus nidulans
o Aspergillus terreus


5. Hyphomycetes
(dematiaceous moulds)

 Sporothrix schenckii



Transmission/ Pathogenesis
1. Dermatophytes
 Can be anthropophilic, zoophilic or geophilic depending on the source (human, animal, soil)
 Spread by contact with arthrospores (thick-walled vegetative cells formed by dermatophyte hyphae) which can survive for months
 Shed from primary host in skin scales and hair
 Invade keratinized structures of the body

2. Yeasts

Candida
 Part of normal skin flora
 Colonizes damaged skin, intertriginous (apposed skin sites which are often moist and chafed), and oral sites - when there is substantial lowering of host resistance


Cryptococcus
Cryptococcosis may involve the skin, lungs, prostate gland, urinary tract, eyes, myocardium, bones, and joints
- var. neoformans
 often found in soil which has been contaminated by bird excrement
 inhalation of airborne cells
 causes lung infection or even CNS involvement
- var. gattii
 Eucalyptus tree and decaying wood forming hollows in living trees

Malassezia furfur
 Common skin inhabitant
 Pathogenicity occurs when yeast change to hyphae form; stimuli unknown

3. Dimorphic Pathogens
Blastomyces dermatitidis
 Inhalation of airborne spores
 Can become widely disseminated in body
 Fungal infection in lungs; may be confused with tuberculosis
 Can produce abscesses

Histoplasma capsulatum
 Grown as hyphae in soil where there are bird’s droppings
 Inhalation of airborne spores, grows as yeast cells
 Survive intracellularly after phagocytosis
 Can produce acute and chronic pulmonary disease

4. Hyphomycetes (hyaline moulds)
Aspergillus sp.
 Inhalation of airborne stages (conidia)
 Causes thrombosis and infarction when blood vessels invaded
 Patial blockage of airways from fungal mass
 Opportunistic infectant

5. Hyphomycetes (dematiaceous moulds)
 Saprophytic fungus, dimorphic
 Infect through trauma; wounds in skin
 cats are the most notable source of transmission of sporotrichosis to humans
 Ulceration or abscess formation in draining lyphatics


Clinical features
1. Dermatophytes
 May cause one or more of the followings: tinea (“ringworm” of) capitis (hair and skin of scalp), tinea corporis (body), tinea cruris (crotch), tinea manuum (hands), tinea unguium (nails), and tinea pedis (feet)
 Lesion; scaling patch with a raised margin
 Itching
 Often dry and scaly
 Sometimes cracks, hair loss
 Inflammation

2. Yeasts
Candida
 May cause nail pathology in some, especially in patients with mucocutaneous candidiasis.
Cryptococcus
 Influenza-like syndrome or pneumonia
 May involve meningitis (if CNS infected)
Malassezia furfur
 Confined to trunks/proximal parts of limbs
 Associated with hypo- hyper-pigmented macules that coalesce to form scaling plaques
 Lesions not itchy

3. Dimorphic Pathogens
Blastomyces dermatitidis
 A flulike illness with fever, chills, myalgia, headache, and a nonproductive cough may occur, which resolves within days
 Depending on the area of involvement, it may include the following signs, although sometimes asymptomatic: Skin lesions, bone or joint pain, pain on urinating and hoarseness
Histoplasma capsulatum
 Symptoms of acute respiratory histoplasmosis, including fever and cough, occur within two weeks of exposure
4. Hyphomycetes (hyaline moulds)
Aspergillus sp.
 Allergic bronochopulmonary reactions

5. Hyphomycetes (dematiaceous moulds)
Development of a papule that enlarges to a nodule and usually ulcerates over a period of 1 to 2 weeks.
 may progress to the lymphatic system and cause the lymphocutaneous form of sporotrichosis if untreated

General Precautions to prevent fungal infections
(though airborne microbes are hard to prevent)


  • clean, disinfect and dress up wounds thoroughly - prevent microbes from entering through wounds
  • personal hygiene: proper wash-up after training to remove the debris of soil that may have stick onto the skin
  • report to military heads if sick: immunosuppressed individuals are more proned to opportunistic infections


References

  1. Book: Medical Microbiology third eition by M., Cedric at. el.
  2. Dermatophytes: http://www.cfsph.iastate.edu > Factsheets > pdfs > dermatophytosis.pdf
  3. Mycology: http://www.mycology.adelaide.edu.au
  4. Blastomyces dermatitidis: http://www.emedicine.com > med > topic231.htm
  5. Malassezia furfur: http://www.anaisdedermatologia.org.br > artigo_imprimir_en.php?artigo_id=10192
  6. Histoplasma capsulatum: http://wonder.cdc.gov > wonder > prevguid > p0000406 > p0000406.asp

Reported by Pei Shan, TG02

Mmic PBL2 Cheng Hong

Possible Viral Diseases that Might Be Contracted (Part 1)


1. Dengue

-Cause by:
--Dengue virus-Flavivirus family

-Transmission:
--By the bite of the Ades aegypti mosquito
--Bites during the day
--Not transmitted from person to person

-Pathogenesis and symptoms:
--Dengue fever (breakbone fever): Sudden onset of fever, skin rash, muscular pain, recovers in about a week
--Dengue hemorrhagic fever: Acute onset, decrease in platelet count, causing hemorrhage under the skin and GI tract
--Dengue shock syndrome: Severe hypotension(low blood pressure), may cause shock, maybe fatal if not treated immediately

-Suitable precaution:
--Wear mosquito repellent on exposed skin area and wear long pants and long sleeve shirt when possible.



2. Hantavirus Diseases


-Cause by:
--Hantaviruses- Bunyaviruses family

-Transmission:
--The virus is carried by rodents
--Humans infected by direct contact/ aerosols from feces, saliva, urine of infected rodents

-Pathogenesis and symptoms:
--Acute viral disease, the virus damage vascular endothelium thus causing hypotension, hemorrhage and shock
--May also cause impaired renal function

-Suitable precautions:
--Avoid exposure to rodents and their excreta
--Ensure tents are free from rodents and their excreta
--Ensure all food is protected from contamination by rodents



3. Japanese Encephalitis

-Cause by:
--Japanese encephalitis virus- Flavivirus family

-Transmission:
--By the bite from the infected Culex mosquito

-Pathogenesis and symptoms:
--Mild infection: febrile headache, aseptic meningitis
--Severe infection: rapid onset, headache, high fever, meningeal signs (50% is fatal)

-Suitable precautions:
--Vaccination available
--Wear mosquito repellent on exposed skin area and wear long pants and long sleeve shirt when possible.



4. Rabies

-Cause by:
--Rabies virus( rhabdovirus)- Lyssavirus family

-Transmission:
--Bites from infected wild animals (bats, wild boar etc)
--Virus present in the saliva

-Pathogenesis and symptoms:
--Infect human when saliva containing rabies virus from animal bite penetrates into skin
--Headache, fever, malaise, numbness on site of bite, hallucinations, spasms, death must occur if not treated immediately

-Suitable precautions and treatment:
--Vaccination available, post exposure treatment also available
--Avoid contact with wild animals, if bitten, clean wound and wash with disinfectant immediately



5. Yellow Fever

-Cause by:
--Yellow fever virus (arbovirus)- Flavivirus family

-Transmission:
--Bite from infective Aedes aegypti mosquito
--Normally bite during the day

-Pathogenesis and symptoms:
--Acute onset, fever, muscular pain, headache, chills, nausea, vomiting, bradycardia
--May proceed to development of jaundice, abdominal pain, haemorrhage (50% of which will die)

-Suitable precaution:
--Vaccination avalible
--Wear mosquito repellent on exposed skin area and wear long pants and long sleeve shirt when possible.


References :
http://www.who.int/mediacentre/factsheets/fs100/en/print.html
http://www.who.int/biologicals/areas/vaccines/yellow_fever/yellow_fever_background/en/print.html http://www.jungleformula.co.uk/jfrange/index.html


*Note: In yen ting's blog she will cover other Part 2, other possible viral diseases

Possible Viral diseases--->Part 2

1. O'nyong'nyong virus

Caused by: Alphavirus of the Togaviridae family
This virus is a small positive sense single stranded nonsegmented RNA virus that replicates in the cytoplasm of cells


Transmission: Anopheles funestus and anopheles gambrae mosquito. It is found in Ades aegypti mosquito vectors in Asia.

Pathogenesis: Sylvatic cycle. Meaning, ades aegypti mosquito bites the human skin and introduces the virus into the bloodstream.

Symptoms: Polyarthritis (arthritis at multiple areas of the joints), rash and low grade fever. Other symptoms that may not may not present includes eye pain, chest pain, lymphadenitis (lymph node inflammation) and lethargy.

Suitable precaution: Note that currently, there are no vaccines available. The best method in prevention is to avoid mosquito bites such as wearing long sleeves and long pants to cover the limbs and to treat clothes with permethrin or alternatively, use insect repellents.


References:

http://www.stanford.edu>group>virus>delta>2005>ovirus.pdf
http://en.wikipedia.org/wiki>O'nyong'nyong_virus


2. Chikungunya

Caused by: Alphavirus of the Togaviridae family which is similar to the o'nyong'nyong virus

Transmission: Ades aegypti mosquito vectors

Pathogenesis: Sylvatic cycle.

Symptoms: Petechial (small red dot) or maculopapular (bumpy bumps) rash around the limbs and trunk. Polyarthritis resulting in debilitating pain causing contortions in affected joints, headache, slight photophobia (sensitivity to light), fatigue, nausea, vomiting and muscle ache. There are many other symptoms depending on age and severity of the disease. Note that the disease is similar to dengue.

Suitable precaution: Same as o'nyong'nyong virus.


References:
http://en.wikipedia.org/wiki>Chikungunya
http://www.cdc.gov>ncidod>dvbid>Chikungunya>chikvfact.htm


3. SARS (
Severe Acute Respiratory Syndrome)

Caused by: SARS coronavirus

Transmission: Spread mainly by close person-to-person contact. When an infected person coughs or sneezes, droplets of mucus or saliva that contain the virus are sent through the air. Once these droplets land on the mouth, nose or eyes, an infection can occour. Kissing, touching, sharing utensils for eating and drinking, or talking with an infected person is also a risk factor for infections. if you travel to countries with SARS. There is no treatment for SARS. Scientists are testing treatments and vaccines.

Pathogenesis:

Week 1: Fever, muscle aches and other symptoms that generally improves after a few days.
Week 2: Patients experiences recurrance of fever, diarrhea and oxygen desaturation (characterised by breathing difficulties) and severe worsening of condition of the patient may occur.
Week 3: Patients requires ventilatory support and some may develop end-organ damage and severe lymphopenia (abnormally low levels of lymphocytes, which is a type of white blood cells) resulting in death.

Symptoms: Patients are present with a high fever of > 38.0°C, including chills, headache, dizziness, rigors (shaking due to high fever), malaise (general feeling of discomfort), muscle aches.

Suitable precaution: Observe hygiene such as frequent washing of hands and avoid sharing of utensils.


References:
http://www.sarsreference.com>sarsref>trans.htm
http://www.sarsreference.com>sarsref>prevent.htm
http://www.sarsreference.com>sarsref>diag.htm


4.Tick borne encephalitis

Caused by: Tick-borne encephalitis virus (TBEV) which is a member of the Flaviviridae family.

Transmission: Tick bites of the ixodes species

Pathogenesis: Ticks are the hosts and the reservoir of the virus. TBEV chronically infects ticks and is transmitted from larva to nymph to adult ticks. TBEV infects humans when tick bites during the peak period of april to november.

Symptoms: Asymptomatic for the first 2 weeks. Non-specific symptoms including fever, muscle aches, anorexia, headache, nausea and vomitting.

Suitable precaution: Vaccination and using insect repellents and protective clothing such as long sleeves, long pants and covered shoes.

References:
http://www.cdc.gov>ncidod>dvrd>spb>mnpages>dispages>TBE.htm


5. West Nile Fever

Caused by: West nile virus of the flaviviridae family

Transmission: Bites of the Culex quinquefasciatus (southeast asia), Culex pipiens (in the US) and Culex tarsalis (in the middle east and europe) mosquito.

Symptoms: There are 3 different effect of the virus on humans.

(a) Serious symptoms -----> neuroinvasive disease known as meningitis or encephalitis where patients may experience
a decreased level of consciousness which may develop into near-comatose stage. Symptoms includes high fever, stiff neck, headache, stupor, disorientation, coma, tremors, convulsions, muscle weaknes, loss of vision, numbness of the limbs and paralysis.

(b) Mild symptoms -----> patient experiences a mild febrile (fever) syndroms known as West Nile Fever. Sypmtoms includes fever, headache, body aches, nausea, vomitting, swollen lymph nodes and rashes appearing around the trunk area.

(c) Asymptomatic


Suitable precaution: Same as o'nyong'nyong virus and chikungunya.

References:
http://en.wikipedia.org/wiki>West_Nile_virus
http://www.cdc.gov>ncidod>dvbid>westnile>wnv_factsheet.htm


6. Influenza (Flu)

Caused by: Family of Orthomyxoviridae viruses known as the influenza viruses.

Transmission: From infected bird droppings, coughing and sneezing of infected person, creating aerosols of the virus and contact with contaminated surfaces.

Pathogenesis: Entry to host cells followed by binding of the host's columnar epithelial cells at the respiratory tract. Fusion with the cell's membrane and release of viral RNA which replicates within the nucleus, synthesizing structural and envelope proteins then releasing virions infecting neighbouring cells.

Symptoms: Fever, extreme coldness, sore throat, muscle pains, severe headache, coughing, weakness, fatigue, nasal conjestion, redden irritated watery eyes, coughing, sneezing and general discomfort.

Suitable precaution: Influenza vaccinations and observe hygiene.

References:
http://en.wikipedia.org/wiki>Influenza

7. Hepatitis A

Caused by: Hepatovirus hepatitis virus (HAV)

Transmission: Contaminated food and water.

Symptoms: Nausea, diarrhea, fever, jaundice, fatigue, abdominal pain, loss of appetite and weight loss.

Suitable precaution: Vaccination and throughly cook food, drink boiled water and observe personal hygiene.

References:
http://en.wikipedia.org/wiki>Hepatitis_A
http://www.cdc.gov>ncidod>diseases>hepatitis>a>fact.htm




Yeng Ting
TG02

Saturday, 19 January 2008

Possible protozoa pathogens - Eunice

Protozoa (vector-bourne/foodborne)

1. Plasmodium species
Widespread in tropical and subtropical regions, including parts of the Americas, Asia, and Africa. Plasmodium vivax and Plasmodium falciparum are predominant in Southeast Asia.

Transmission
· Infection is initiated following a bite from a female anopheline mosquito.

Pathogenesis
· When an infected mosquito pierces a person's skin to take a blood meal, sporozoites in the mosquito's saliva enter the bloodstream and migrate to the liver
· sporozoites infect hepatocytes, multiplying asexually and asymptomatically into numerous merozoites which would rupture from liver cells to the circulatory system to infect RBCs.
· Within the red blood cells, the parasites multiply from merozoites into trophozoites (ring form) then into schizont.
· Some P. vivax and P. ovale sporozoites may develop into hypnozoites that remain dormant for periods.
· After mature schizont formed, RBCs rupture releasing merozoites and the newly released meozoites will repeat the whole cycle by infecting other RBCs.

Symptoms
· fever, shivering, arthralgia (joint pain), vomiting, anaemia caused by hemolysis, hemoglobinuria, and convulsions.
· severe malaria may cause coma and death if untreated, splenomegaly, severe headache, cerebral ischemia, hepatomegaly, hypoglycemia, and hemoglobinuria with renal failure may occur.

Precaution
· Wear long sleeves and long pants; sleep in sleeping nets if possible.
· Application of mosquito repellent.


2. Toxoplasma species
Toxoplasmosis is a parasitic disease caused by protozoan Toxoplasma gondii. The parasite infects most warm-blooded animals, including human.

Transmission
· Ingestion of raw/ partly cooked meat containing Toxoplasma cysts.
· Drinking water contaminated with Toxoplasma

Pathogenesis
· Ingestion of oocytes or tissue cysts in improperly cooked meat becomes infected.
· The parasite enters marcophages in the intestinal lining and is distributed via the blood stream throughout the body.
· Focal areas of necrosis may develop in a variety of organs and the clinical manifestations reflect injury to specific tissues.

Symptoms
· influenza-like: swollen lymph nodes, or muscle aches and pains that last for a month or more.

Precaution
· ensure food are well-cooked
· avoid contact with rodent and its excreta
· wash utensils and hands before handling food


3. Helminths – Wuchereria bancrofti
Itis a parasitic filarial nematode worm spread by a mosquito vector It is one of the three parasites that cause lymphatic filariasis. Can be found in tropical and sub-tropical countries.

Transmission
· disease spread by mosquito bites
· All worm offspring are passed on through poorly cooked meat, especially pork, wild fish, and beef, contaminated water, feces, mosquitoes and, in general, areas of poor hygiene and food regulation standards such as parts of Africa, Central and South America and Asia

Pathogenesis
· The microfilaria are present in the circulation. The microfilaria migrates between the deep and the peripheral circulation.
· During the day they are present in the deep veins and during the night they migrate to the peripheral circulation.
· the worm is transferred into a vector; the most common vectors are the mosquito species: Culex, Anopheles, Aedes, and Mansonia, and when current host feeds, and it is egested into the blood stream of its new human host.
· The larvae moves to the lymph nodes, predominantly in the legs and genital area, and develops into adult worm over the course of a year. By this time, an adult female can produce microfilariae itself.

Symptoms
· swelling, granulation lesions, and impaired circulation, the lymph nodes are enlarged and dilated.
· affected tissue will expand and elephantiasis, will result, followed sometimes by death.

Prevention
· Wear long sleeves and long pants; sleep in sleeping nets if possible.
· Application of insect repellent.


4. Leishmania species
Leishmania is a genus of trypanosome protozoa, and is the parasite responsible for the disease leishmaniasis. Leishmaniasis can be transmitted in many tropical and sub-tropical countries

Transmission
· transmitted by the bite of certain species of sand fly

Pathogenesis
· Bite of female phlebotomine sandflies will inject the infective stage, metacyclic promastigotes, during blood meals.
· Metacyclic promastigotes that reach the puncture wound are phagocytized by macrophages and transform into amastigotes which will multiply in infected cells and affect different tissues.

Symptoms
· fever, damage to the spleen and liver, and anaemia.


Foodborne protozoa
Gardia, Cryptosporidium and Cyclospora (covered in elaine's post) are intestinal protozoan parasites that parasitise in both human and non-human host. There is increasing evidence that these organisms are significant contaminants of food.
Food consumed raw or lightly cooked, with viable oocytes has been responsible for several outbreaks of giardiasis, cryptosporidiosis and cyclosporiasis.


References:
http://en.wikipedia.org> malaria parasite
http://en.wikipedia.org> toxoplasmosis
http://en.wikipedia.org> helminths> wuchereria bancrofti
http://en.wikipedia.org> leishmania

Book: Foodborne pathogens: hazard, risk analysis and control / edited by Clive de W. Blackburn and Peter J. McClure

Water borne protozoa_elaine

Protozoa: single-celled parasites

Infection with parasites is a major cause of morbidity and mortality in tropical and semitropical countries

Transmission:
--faecal-oral
--arthropod vectors
--intermediate hosts e.g. fishes or snail


1) Giardia Lamblia (giardiasis): A flagellated protozoon and an important cause of diarrhea worldwide.
http://www.brown.edu/Courses/Bio_160/Projects2004/rotavirus/Epidemiology.htm

[Route of infection]: Faecal-oral

[Pathogenesis]: cysts of Giardia Lamblia have been demonstrated in the drinking water. Ingestion of cysts—the resistance, infective stage—is followed by the production of trophozoites in the upper small intestine. Trophozoites cause irritation, which leads to gastrointestinal symptoms.

[Clinical features]
Symptoms: diarrhea, mild to severe, with characteristic light-coloured fatty tools; abdominal pain: cramps, with flatulence and epigastric tenderness; anorexia
Malabsorption: steatorrhoea is not common and may lead to the full-blown malabsorption syndrome.

[Precaution]
Consume only treated water sources.

2) Cryptosporidium Parvum (Cryptosporidiosis): human infection is often acquired as a result of animal slurry contaminating water supplies.

[Transmission]:
The infective stage is the oocyst, passed in faeces: transmitted person-to-person, animal-to-person or via contaminated water.

[Clinical features]
Symptoms: self-limiting diarrhea in the immunocompetent individual.

[Precaution]
Consume only treated water/clean water

3) Isospora Belli: humans seem to be the only host of this parasite, which infects the small intestine.

[Transmission]
Faecal-contaminated food and water

[Clinical Features]
In the immunocompetent infection is often asmptomatic and the diarrhea, when present, tends to be mild.

[Precaution]
Consume only treated water/clean water

4) Cyclospora Cayetanensis (Cyclosposiasis): infect the small intestines

[Transmission]
The infective stage is the oocyst passed in faeces (waterborne)

[Clinical features]
Symptoms: diarrhea, remitting and relapsing, sometimes lasting as long as 6 weeks; malabsorption in some cases; weight loss

[Precaution]
Consume only treated water/clean water

5) Entamoeba Histolytica (amoebiasis): a common infection in tropical countries such as Indonesia where the sanitation is poor.

[Route of infection]
Faecal-oral, owing to contaminated water

[Clinical features]
Diarrhea, progressing rapidly to bloody diarrhea accompanied by fever and painful abdominal cramps, symptoms may pesist into a chronic relapsing state. Sometimes progresses to dilatation of the colon, with the risk of intestinal perforation.

[Complication]
Amoebic absecess owning to spread to the liver causing painful enlargement and accompanied by high fever, raised white cell count and high ESR.

[Precaution]
Consume only treated water/clean water



References:
Book: Medical microbiology 4th edition. written by patrick R. Murray, Ken S. Rosenthal, George S. Kobayashi, Micheal A. Pfaller


Book: microbiology of waterborne disease. written by S L Percival, R M Chalmers

Wednesday, 16 January 2008

MMIC - PBL2. Avian Flu

Avian Influenza (Bird Flu):

Pathogen involved: Avian influenza viruses (RNA viruses)



commons.wikimedia.org > wiki > Image

· Typically carried by wild migratory birds in their intestines, which are immune to them. However, it is highly contagious amongst birds, and can infect domesticated birds, that usually fall severely ill.
· Several strains exist:
Denoted by “H" and “N”. “H” stands for hemagglutinin and “N” stands for neuraminidase, two proteins on the surface of the virus that allow it to enter and exit host cells.
o Sixteen different hemagglutinins and nine different neuraminidases have been identified to date.
o Typically, most avian flu is restricted to bird to bird transmission. The most deadly being H5N1 strain as it can spread from bird to human.

Indonesia has had outbreaks of H5N1 viruses, mainly from the poultry breeding farms. Typically, H5N1 transmission is from bird to humans. However in 2006, there was a case of human to human transmission of H5N1 versus between a group of small families, but the spread appears to have died off. H5N1 can last indefinitely at a temperature dozens of degrees below freezing.

Pathogenesis:
Spread to humans via contact, potentially airborne (incubation period is longer, less adapted to droplet transmission):
· Directly from birds or from avian virus-contaminated environments to people (consumption of poultry products, direct contact with live poultry – bodily fluids such as blood, salvia etc and contaminated food sources).
· Through an intermediate host, such as a pig.
Typically develops 1 to 5 days following exposure.

Signs and symptoms:

Common:
- Cough
- High fever (typically > 38°C)
- Headaches
- myalgia (muscle ache/pain)
- malaise (general discomfort)
- Sore throat
- Shortness of breath
- Diarrhoea
- A relatively mild eye infection (conjunctivitis), sometimes the only indication of the disease.

Severe signs and symptoms:
- Viral pneumonia
- Acute respiratory distress (the most common cause of bird flu-related deaths)
- Seizures

Necessary precautions:
· Avoid contact with live birds, and all forms of poultry:
- Chickens, ducks, turkeys and geese and their feces, feathers and pens if at all possible.
· Avoid poultry products in Indonesia, as cases of H5N1 have been reported there.
· All foods from poultry, including eggs should be cooked thoroughly. Egg yolks should not be runny or liquid. Influenza viruses are destroyed by heat, hence cooking temperature for poultry meat should be 74oC (165 F).
· Avoid cross contamination of other foods by use of separate kitchen utensils and surfaces exposed to raw poultry.
· Wash hands with soap and water after any poultry contact.
· Avoid live food markets.

Treatment:
A) Antivirals:
Suppress virus, keep it from replicating and infecting within the host. Must be taken soon (often within 48 hours following infection).
· Neuraminidase inhibitor:
Mode of action consists of blocking the function of the viral neuraminidase protein, preventing the virus from reproducing.
1. Relenza
2. Tamiflu

B) Vaccination:
Vaccines expose an individual to a weakened/dead virus to stimulate antibody production against it, so that immune system can fight off infections should it arise.
· There are at least 15 different strains of avian flu and they are constantly mutating, hence vaccination may not prove to be effective for long.
1. Live vaccines (attenuated, weakened):
- Requires less antigen (active ingredient) than killed vaccine.
- Live vaccine may contain too few copies of the weakened virus to trigger an immediate immune response.
- However, once inside the host, the virus can replicate to render it detectable by the immune system and trigger an immune response.
- Does not require injection – oral consumption will do.
2. Killed virus (inactivated):
- Must be injected – only route to administer them that will bring them into contact with the immune system.
Requires larger dosage than live vaccines due to its lack of ability to multiply within host.
3. Recombinant vaccine:
- Genetically engineered vector (usually a low virulence virus) to express H5N1 protein antigen on surface, to stimulate immune response (production of antibodies).

References:
sciencedaily.com > releases > 2007 > 08/070828154944.htm
cidrap.umn.edu > cidrap > content > influenza > avianflu > news > dec3005halvorson.html
evolution > berkeley.edu > evolibrary > news > 51115_birdflu
http://www.cbc.ca/> news > background > avianflu > protection.html

Cheers,

Debra, TG02