Biology 261

- Rabies is caused by a rhabdovirus, a negative-strand RNA virus that infects cells in the central nervous system of most warm-blooded animals, almost invariable leading to death if not treated.

- Negri bodies: fluorescent antibodies in nerve cells.

- All dogs and cats should be vaccinated against rabies beginning at 3 months of age, and booster inoculations should be given yearly or every 3 years.

• • “Four corner” disease, traced to the deer mouse as a natural reservoir. Other rodents also serve as
• reservoir.

• In 1993 outbreak 32 deaths in 53 affected adults.

• A member of Bunyaviridae, negative strand RNA virus.

• • Cause either hantavirus pulmonary syndrome (more
• typical in Western Hemisphere) or hemorrhagic fever with renal syndrome (common
• in Asia).

• Humans are infected through exposure to dry urine and feces of rodents.

• Death is within 5 days

• • Typical detection is
• with ELISA or by RT-PCR

• • No treatment or vaccine.
• A BSL-4 pathogen.

• Rickettsia are closely related to mitochondria and contain several virulence genes.

• • Typhus fever - Rickettsia prowazekii. Transmitted through body or head louse bites. 3 million death
• in WWI. Epidemic typhus mortality can reach 6-30%. Treated with tetracycline
• and chloramphenicol. Vaccine is available.

• • Rocky Mountain spotted fever - Ricketsia ricketsii. Transmitted through injection of tick fecal
• matter during tick bites. Mortality 1-30%. Treated with tetracycline and
• chloramphenicol.

• Human monocytic ehrlichiosis - Ehrlichia chaffeensis and Neorickettsia sennetsu. Human granulocytic anaplasmosis (ehrlichiosis) - Ehrlichia ewingii and Anaplasma phagocytophilum. Both transmitted by ticks. Deer and rodents are additional reservoirs. Flu –like symptoms. Treatment with doxycycline.

• • Q fever - Coxiella burnetii. Transmitted from animal to animal through insect bites. Humans become infected through contact with animals and animal products. Flu-like infection, treated with
• tetracycline.

• • Diagnosis of rickettsial diseases with fluorescent antibodies, the presence of specific antibodies in
• blood (ELISA, latex bead agglutination) or PCR.

•Control through control of lice, fleas and ticks.

•Spirochete - Borrelia burgdarferi, which is spread by the deer tick.

• Natural tick’s hosts are deer and white-footed field mouse.

• Most frequently found in northeastern regions of the United States (see next picture).

• Headache, backache, chills and fatigue. A large rush, erythrema migrans, is observed in 75% of cases. At this stage disease is easily treatable with tetracycline and penicillin.

• • If progresses to chronic stage, arthritis (40-60%), neurological damage (15-20%) and cardiac damages
• (8%) may occur. Ceftriaxone is used to treat chronic Lime disease.

• • Detection of antibodies to Borrelia burgdorferi with ELISA, fluorescent antibody assay,
• immunoblot, PCR. Can be cultured in 80% of cases.

• No effective vaccine is available. A recently available vaccine has been pulled off the market.

• Prevention: tick control and personal precautions.

•350 million people are infected with malaria and 1 million dies every year.

•Four species of protozoan belonging to the Sporozoa phylum. Plasmodium vivax is most common, Plasmodium falciparum is most deadly.

• Transferred through bites of Anopheles mosquitoes, which prefer a hot climate and require water for breeding.

• Diagnostics: microscopic observation of malaria cells in erythrocytes.

• •Prophylaxis and treatment with chloroquine and primaquine and lariam (mefloquine). Melarone
• (atovaquone and proguanil) is used for drug resistant strains. Doxycyline can
• also be used for prophylaxis.

•Control of malaria: (1) elimination of habitat, (2) elimination of mosquitoes.

• Despite control, endemic malaria still exists in the US.

• Circle cell anemia

• – Mutation in a beta chain of hemoglobin, valine is replaced with glutamic acid. Resulted hemoglobin is
• called hemoglobin S.

• – Under low oxygen condition hemoglobin S form long chains change the shape of erythrocytes. P.
• falciparum cannot grow in such erythrocytes.

• Glucose-6-phosphate dehydrogenase deficiency in some areas in Italy.

• Thalassemias in Mediterranean populations lead to protection against P. falciparum.

• •One specific MHC I and MHC II genes are expressed in some individuals in West Africa making them
• resistant to malaria

• Killed 25% to 33% of Europe population during the Middle Ages.

• Natural disease of domestic and wild rodents (see next picture). Endemic in the southeastern states of the US.

• Transferred by rat fleas.

•Once infected Y. pestis travels to lymphatic nodes and form buboes. If not treated death occurs within 3-5 days.

Pathogenesis is not clears. The V and W antigens inhibit phagocytosis. Murine toxin is an exotoxin produced by virulent strains. Endotoxin plays important

• The epidemiology of plague due to Yersinia
• pestis. Plague in most wild rodents is generally a mild, self-limiting infection. Plague in rats and humans is frequently fatal. Infected fleas desert the dead host and look for other hosts, such as humans, an accidental
• host.

• •Treatment: If treatment started promptly, mortality is 1-5%. Treated with streptomycin, tetracycline
• and ciprofloxacin.

• Control: surveillance of infected animals vector and human contacts.

• Vaccine is available.

• Yeasts or molds, only 50 species cause diseases in human.

• Hyperallergic response. Aspergillus spp.

• Mycotoxin production, Aspergillus flavus

• Mycosis

– superficial mycosis

– subcutaneous mycosis

– systemic mycosis

• primary and secondary infections

• A primary mycosis - direct infection with a fungal pathogen.


• A secondary mycosis - in immunosuppressed individuals or following therapy with antibiotics.

•In the US most common mycoses are:

• Histoplasmosis caused by Hisptoplasma capsulatuim, Ohio and Mississippi river valleys,

• • Coccidioidomycosis caused by Coccidioides immutis
• (San Joaquin Valley fever).

• Infected by inhalation, particularly serious infections in AIDS patients.

• Treatment: amphotericin B.

• Caused by Clostridium tetani

• Infection through contaminated wound, usually a deep puncture

• C. tetani produces an exotoxin, the tetanus toxin

• A vaccine is very efficient

• Treatment: antibiotics, usually penicillin, antitoxin and support therapy. Once disease developed, morbidity and mortality are very high despite treatment.

•Caused by Clostridium tetani

• Infection through contaminated wound, usually a deep puncture

• C. tetani produces an exotoxin, the tetanus toxin

• A vaccine is very efficient

• Treatment: antibiotics, usually penicillin, antitoxin and support therapy. Once disease developed, morbidity and mortality are very high despite treatment.

• West Nile fever or encephalitis.

• Active disease in birds (more than 150 species) , can be transferred to human and horses by mosquito bites.

•Human mortality is 4%, for horses it is up to 40%.

• Adults over age 50 are most susceptible.

• Diagnosis by ELISA and RT-PCR.

• No specific treatment, prevention is a control of the vector.