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Multisystem Zoonoses Reading: pg. 401 – 412Introduction• Zoonoses: animal diseases that may be transmitted to humans• animal is host reservoir• human infection is incidental• disease is usually not transmitted human to humanArenaviruses• transmitted to humans in rodent excreta• Arenaviruses and the diseases they cause (fig. 28.2)• diagnosed serologically, by viral isolation or molecular techniques• Lymphocytic choriomeningitis virus (LCM)• Cause sporadic infection in people• Mild febrile illness, could lead to aseptic meningitis• Lassa fever– caused by exposure to infected rats or their urine– rat to human disease usually mild– human to human disease more severeArenaviruses• transmitted to humans in rodent excreta• Arenaviruses and the diseases they cause (fig. 28.2)• diagnosed serologically, by viral isolation or molecular techniques• Lymphocytic choriomeningitis virus (LCM)• Cause sporadic infection in people• Mild febrile illness, could lead to aseptic meningitis• Lassa fever– caused by exposure to infected rats or their urine– rat to human disease usually mild– human to human disease more severeKorean hemorrhagic fever• Cause Hantaan virus• bunyavirus• transmitted to humans in rodent urine• Causes harmless infection in mice and rats• In human - Febrile illness, with hypotension, hemorrhage, and renal syndromeMarburg and Ebola hemorrhagic fevers• Cause filoviruses• Symptoms: fever, hemorrhage, rash, disseminated intravascular coagulation• reservoirs of origin unknown for both viruses• no treatment• no vaccine• high mortality rate• Marburg – can be transmitted by semen for months after recovery• Ebola – transmitted person to person in hospitalsQ fever• caused by Coxiella burnetti, a rickettsia• infects livestock• carried by arthropods but actually transmitted to humans by inhalation• Transmitted via placenta of infected animals, unpasteurized milk and tissue fluids• diagnosed serologically – complement fixation• treated with tetracylines in acute phase• treated with rifampin and doxycycline or trimethoprim-sulfamethoxazole in chronic cases• killed by pasteurization• vaccine available for those at riskAnthrax• caused by Bacillus anthracis• primarily a disease of livestock (herbivores)• Bacteria excreted in feces, urine, saliva• Transmitted to humans by direct contact• Enter body through skin, mucous membrane, respiratory tract• forms a black eschar (fig. 28.4)• fatal if untreated• Septicemia à generalized toxic effects, edema and death• diagnosed by gram stain and culture on blood agar• treated with penicillin• Or chloramphenicol and erythromycin• mainly a disease of developing countries• Due to vaccination of animals and humans who are at riskPlague• caused by Yersinia pestis, encapsulated• rodents are the animal reservoir• spread to humans by fleas (fig. 28.5)• clinical features include buboes and pneumonia• high mortality rate• 50% in untreated bubonic plague• 100% in pneumonic plague• diagnosed by gram stain and culture• treated with streptomycin and/or tetracycline• plague prevention• Quarantine measures, rodent control, chemoprophylaxis• vaccine availableYersinia enterocolitica• Causes diarrheal disease• rodents, rabbits, pigs and other livestock are reservoirsTularemia• caused by Francisella tularensis, Gram negative rods• spread among animals by arthropod vectors• human infection from contact with animal carcass (skinning of infected animals) or bite of arthropod vectors• Clinical features: swollen lymph nodes, febrile illness• Blood invasion à lungs, GI tract and liver• diagnosed serologically• not cultured because of high risk of laboratory infection• treated with streptomycin, vaccine available for those at high riskPasteurella multocida• Gram-negative, encapsulated rod• normal flora of cats and dogs• transmitted to human by animal bite and scratches• diagnosed by microscopy and culture• treated with penicillinLeptospirosis• caused by Leptospira interrogans (fig. 28.7)• many wild and domesticated mammals are reservoirs• Infection leads to chronic kidney infection à organism excreted in urine• humans infected by contaminated water or food• infection can also occur by body exposure to contaminated water or food• Clinical features: kidney and liver failure, aseptic meningitis or conjunctival hemorrhage• diagnosed by microscopy and serologic tests• treatment is penicillin and tetracycline• doxycycline effective in exposure preventionRat bite fever• caused by:• Spirillum minor – Gram-negative spiral• Streptobacillus moniliformis – Gram-negative filamentous bacillus• reservoir is rodents including laboratory rats• Transmission to humans by bites• diagnosed by microscopy and culture• treated with penicillin or streptomycinBrucellosis• caused by Brucella melitensis which has four variants• Gram-negative, coccobacilli• 4 strains:• B. abortus – infects and causes abortions in cows• B. mellitensis – infects goats and sheep• B. suis – infects pigs• B. canis – infects dogs• infects livestock (fig. 28.9)• Cows, pigs, and goats – causes abortions• Humans – contact with infected animals and their products• symptoms are immune-mediated• diagnosed by serologic tests and culture (takes up to 4 weeks)• treated with tetracycline, streptomycin or co-trimoxazoleHelminth infections• Echinococcus• Trichinella• Strongyloides
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