Question

There are many pathogens out there and new ones emerging all the time. Do some research and choose a particular pathogen that interests you. Review its virulence, the common diseases produced by it, and the possible treatments for the diseases and share this information with the class. Some examples could be any mosquito or tick-borne illnesses that affect humans. Also, there is an increase in pathogens affecting animal populations that you may research.

Answer 1

Name of the pathogen - Rickettsia prowazekii

Disease caused by it - Epidemic typhus

Vector - body louse ( pediculosis humanus corporis)

Reservoir - Humans, southern flying squirrel (Glaucomys Valons)

Risk factors

1. Outbreaks occur where there is overcrowding. Example - camps, barracks, prisons
2. Winter seasons.
3. Poor hygiene
4. Developing nations of Asia, Sub-Sahara, Latin America

Modes of Spread

1. From human to human only through the agency of body louse.
2. In the absence of the body louse, no human to human transmission can occur.
3. Through the feces of the louse, the bacteria can enter through the breach in the skin
4. The bacteria can survive in the feces of the louse and the dead louse for 100 days.
5. Inhalation of the fecal matter of the louse.
   • The body louse becomes infected with the bacteria on feeding on the blood of infected patients of epidemic typhus.
   • They lice start excreting the bacteria in their feces after 2-6 days.
   • If this infected louse is transferred to another individual, it will start excreting the bacteria in the feces.
   • These bacteria containing feces can enter the patient's body through cracks in the skin, or scratch marks.

Incubation period: 1 - 2 weeks,

Clinical features -

1. Headache, fever, chills, myalgia
2. Rash ( present only in some)
   1. small pink macule present on upper trunk and armpits
   2. Then can spread all over the body
   3. Face, palms, soles spared.
3. Cough ( secondary pneumonia)
4. Petechiae on conjunctiva and palate
5. Joint pain
6. Abdominal pain
7. CNS
   1. confusion
   2. Drowsiness
   3. Coma
8. Vasculitis can lead to gangrene of toes and fingers.
9. Acute febrile stage lasts for 2 weeks - later resolves over 2 - 3 months
10. It can recur ( recrudescent typhus) after years and usually a milder disease. (Brill- Zinsser disease)

Diagnosis:

1. Serology -
   1. a four-fold rise in titer
   2. this test comes positive in 2nd week
   3. Indirect Immunofluorescence test, latex agglutination test, ELISA
   4. Complement fixation test
2. Organism demonstration -
   1. in the tissue sample by Immuno-histochemistry
   2. PCR - polymerase chain reaction test.

Disinfection - The organism is susceptible to

1. 1% sodium hypochlorite
2. 70% ethanol
3. 3 - 6% hydrogen peroxide
4. The Organism is killed by heating (121 degree moist heat, 170 degree dry heat)
5. Bathing regularly kills the bacteria.

Treatment - Doxycycline for 7 - 10 days.