ZOONOSES(Block I posting Medical & Dental Students )

Definition: Zoonoses are diseases mainly of vertebrate animals that can also be transmitted to man.

The animal may either be asymptomatic or symptomatic.

Mode of Transmission:The knowledge of the mode of transmission is a prerequisite for effecting prevention and control of disease.Direct contact: The occupation of an individual may enhance direct contact with animals and their products eg. Farming, animal husbandry, etc.Diseases such as brucellosis, anthrax, Q fever, toxoplasmisis, erysipeloidmay be contacted.Inhalation: of aerosols of infected animal excreta, secretions or other productseg. Q fever, brucellosis, pulmonary anthrax.

Mode of Transmission-2:Ingestion of infected food and milk product eg. Meat, fish, eggs, milk and dairy products, eg. Unpasteurized milk as a sources of zoones

Unpasteurized milk as a sources of zoones

DISEASES ORGANISMS Tuberculosis (bovine)Mycobacterium tuberculosis, bovis.BrucellosisBrucella abortus (cattle)Brucella melitensis (sheep & goat)SalmonellosisSalmonella typhimuriumSalmonella dublinOther salmonella species Q feverCoxiella BurnettiListerosisListeria monocytogenesCampylobacter InfectionCampylobacter jejuni

Mode of Transmission-3:Saliva - as a result of bites or licks from infected animals eg. Rabies, rat-bite fever.Feaces:- contaminating foods, soils or surfaces.inhaled as droplets, eg. Salmonellosis, hydatid, toxocaria or ornithocosis.Urine: Leptospirosis - direct infection - indirectly while swimming

Mode of Transmission-4:Blood and tissueslab workers, Zoo workers etc.

Arthropod vectors.

Bacterial ZoonosesTuberculosisOrganisms may be present in milk. Human acquire the infection by drinking the infected unpasteurized milk, resulting in infection of the cervical glands and abdomen (TB. Abdomen).SalmonellosisSources - poultry, cattle, pigs, rodents, chickens and turkeys are good reservoirs of infection.

Bacterial Zoonoses-2BrucelosisCausative organisms: Brucella abortus from cattle Brucella melitensis from goats and sheeps Brucella suis from pigs.

Brucella abortus

predilection for erythritol in bovine (but not in human) placentalocalized in mammary glands of cattle - a source of infection to man.Farmers, vets - acquire infection by direct contact with product of conception of cattles.drinking unpasteurized milk from infected cows.Laboratory accidentsAbraded skin, conjunctiva or alimentary tract are other portals of entry.

Brucella melitensis

Causes Mediteranean or Malta fever:

Frequently present in unpasteurized milk or cheeze products from goat and sheep in Mediteranean and Middle East countries.

Brucelosis: Pathogenesis

Organisms are intracellular parasites of RES in bone marrow, liver, spleen lymphnodes. From these sites the bacteria pass into the blood.No person to person spread.

Brucelosis: PresentationAcute BrucellosisIncubation period : 2 - 3/52 due to Br. melitensis but mainly Br. abortus.high fever, headache, sweating, fatigue, join pains, splenomegalySubacute brucellosisdue to persistence of infection with Br. abortus for more than 1/52recurrent attacks, lassitude in apparently well-looking patient.Chronic brucellosis last for many months or yearsrecurrent episodes of headache, flu-like illness, lassitude, anxiety and depression

Subclinical brucellosis also occurs where there is no active infection but patient has raised antibody titres. This is common in Vets and farmers.

Brucelosis: Complication

Death by suicideEndocarditisThrombophlebitisMeningoencephilitisChronic arthritisGranulomata in liver, bone marrow & spleen

DD at this stage is Sarcoidosis.

Brucelosis: Laboratory Diagnosis

Low Blood Counts - with characteristic neutropenia and a lymphocytosis.Blood culture - positive in 20% of cases, Br. metilensis is easier to cultivate than Br.abortus which requires increase CO2 in atmosphere.The Organism are Small GN non-capsulated, coccobacilli or short rods.Liver biopsy for isolation and histology in Blood culture negative cases.

Brucelosis: Laboratory Diagnosis-2Serology: Standard agglutination testPaired sera to demonstrate a rising titre (> 4 fold) of brucella agglitinins, in standard phenol - saline agglutimin tests.Actute - High titres in 2nd - 3rd wk. (> 1/80).Subacute and chronicdifficult interpretationother test:1.2-mercapto ethanol test2.Brucella complement fixation test (CFT)3.Anti - human globulin test (AHG or Coombs test)

Brucelosis: Rx:

1.Tetracycline + Streptomycin x 1/12, Thereafter tetracycline x 1/12

2.Cotrimoxazole x 2 -3/12

Brucelosis: Prevention

Pasteurization of milkVaccination of female calvesMonitoring of cattle for infection (milk-ring test with a acethylene blueStained antigen to detect antibody in milk).Eradication of brucella-infected cattle.Protective clothes, goggles for vets.

Leptospirosis

Animal reservoir of leptospiraSmall wild animals such as rodents, volvesLarger farm on domestic animals such as pigs, cattle and puppies.

Habitat: Stagnant water and wet soil especially when pH is alkaline contamination by infected animal urine.

Classification:Order Spirochaetales.Family Leptospiraceae.3 genera Leptospira (the only pathogenic to animal and man).Leptonema.Turneria.

Leptospira: two speciesLeptospira interrogans comprises the parasitic and pathogenic leptospires. It has 23 serogroups, eg Leptospira icterohaemorrhagiae; Leptospira hardjo.Leptospira biflexia contains all strains found in the environment but cause no disease.

Leptospires6 - 20m long, 0.1m diameterPasses through filters.Gram-negative, stains poorly.Visualised by Giemsa or silver impregnation.Best vied by dark-ground or electron microscopy.

Cycle of Infection: may involve more than one animal species

Leptospira spirochactes in wet source penetrate abraded or intact skin or conjunctiva, Mucous membrane of new animal host or man.Invasion of blood and localize in sites eg. Kidneys, resulting in Leptospiruria which maintains the cycle.Human to human spread rare.A vasculitis resulting in damage to endothelial cells of small blood vessels.

Leptospirosismajority asymptomaticPeople at risk of infectionwet occupation eg. Rice farmers, minersLeisure seekers - swimming in contaminated water, playing with infectedPet dog.Incubation period : 7 - 12 days

Clinical featuresInfluenza-like illness characterised by sudden onset ofHeadache.Muscle pain (lower back & calf)Fever, occasional rigor.Conjunctival suffusion.Skin rash.

Clinical featuresSevere cases may follow a biphasic course: =>Bacteraemic followed by=> immune phase:- return of severe headache, rigor & meningism. Bleeding; jaundice & renal impairment.Typically, bilirubin concentration is markedly raised.Other LFTs also raised.Prognosis good with adequate prompt Rx.

3 main serogroups of leptospira

Leptospira canicola serogroup (canicola fever infection in children playing with puppies, pigs).Leptospira icterohaemorrhagiae sero group/reservoir - rats.Weil's diseaseClassical characteristics - fever, jaundice subconjunctivalHaemorrhages and proteinuriasevere heptonenal failuredeathLeptospira lebdomadis serogroup - cattle, field mice volves.

Lab. Diagnosis

Dark-ground microscopyBloodUrineBlood culture - positive during first weeks of illness.=>Special culture media such as Fletcher's or Korthoff's media=>Guinea-pig inoculation.Urine culture - positive result during 2nd week.Serology - CFT and Micro-agglutinins

Rx: - Benzyl penicillin Tetracycline/erythromycin in penicillin- allergic patients (within 4/7 disease).Prevention:-Protective clothing for those at occupational risk

Rodent control

Disinfection of infected premises

Prophylatic Benzylpenicilline for those with cuts, abrasions.

AnthraxBacillus anthracis - aerobic Gram - positive spore-forming bacillus.Anthrax is a disease primarily of sheep and cattle.Spores - survive for many years in contaminated soil infectionmainly an occupational hazard in handless of contaminated hides, hair and products of cattle, the wool of sheep and bone real

Anthrax : Presentation

A)Cutaneous anthrax characterized by "Malignant pustule'Coagulation necrosis of the centre of the pustule result in the formation of

a dark eschar, which is later surrounded by

a ring of vesicles containing serous fluid and

an area of oedema and induration.

Anthrax : Presentation

B) Pulmonary anthrax ("woolsorter's diseases) high mortality due to:-

=>intense inflammation.

=> haemrrhage.

=> septicaemia.

Anthrax :DiagnosisSwab on BARx: Penicillin

PreventionvaccinationBurrying infected animal in quick hire.

Listeriosis

Listeria monocytogenesGPB sometimes confused with streptococci or diphtheroids.Causes infection in different animal species - cattle, pigs, rodents, birds fish andOccasionally man is infected.Habitat - faeces of animals, soil.Infection => by direct contact=> eating soft cheeses => sexually.

Listeriosis : Clinical syndromes

1.Perinatal listeriosisInfluenza like illnesAcquired during pregnancy rarely cause stillbirthPrematurity with granulomatous pneumoniae Respiratory distress and septicaemiaNeonatal meningitis after 5/7 of birth.2.Febrile illness in vets, abattoir workers, butchers, poultry workersOr other farm workers DD. Influenza.PUO, pneumonia or meningo-encephalits in immunocompromise adults.Splenectomized patientsLymphoma

Listeriosis :Lab. DiagnosisBlood cultureCSF cultureSkin lesion -> cultureHVS in mothers with Neonated meningitisUsing BA.Rx: AmpicillinAmpicillin and Genticin for mothers

Plaque

Yersinia pestis (plague bacillus)a short GNB, non-sporing, non-motileOccurs singly, in pairs or, when in liguid culture, in chains.Pleomorphic.- Grows aerobically & anaerobically at 0-37oCReservoir - Rodents esp. ratsRattus rattus ( black rats)Spread - Rat to rat - Rat to humanVector - Rat flea Xenopsylla cheopsis.

PlaqueIncubation period 2 - 6 daysBubonic Plaque: tender lymphadenopathy esp. the inguinial FebrileSpread - blood HaemorrhageDeath - the Black Death.Pneumonic plaqueSpread - from person to person in epidemic plaque by respiratory droplets

PlaqueLab. DiagnosisSputumLymph node aspirate M/C/SCharacteristic GN bipolar staining coccobacilliBA prolong cultureRx: 1) Streptomycin 2) Chloramphenicol 3) TetracyclinePreventionQuarantine measureRodent control

Viral Zoonoses

RabiesLassa feverMarburg virus diseaseYellow feverNewcastle disease

Rabiesa lethal form of encephalitis.Due to rabies virus which affects a wide range of animal species.Transmitted via the bite of an infected animal but not always a dog.Clinical featuresIncubation period: long usually from 4 to 12 weeks , may even be longer. The nearer the wound is to the head, the shorter the IC.Spread : wound to CNS via nerves.

Symptoms: excitement, tremor, convulsions, spasm of muscles of swallowing (hydrophobia).Prognosis: fatal, death following a convulsion.Pathology: main changes are the typical intracytoplasmic inclusion within neurones known as Negri bodies.In West Indies and Central and South America, anther type occurs as ascending myelitis with paralysis and lesions are found in the ganglion cells of the spinal cord. It is spread by the bite of infected vampire bats.

RabiesEpidemiologyRabies is a natural infection of dogs, cats, bats and carnivorous wild animals such as foxes, wolves, it sometimes affect cattle.Vehicle of transmission: saliva of infected animals.Incidence: few.

Rabies -Virology:Rhabdovirus; one serotypeRNA virusBullet shape; enveloped , helical-coiled nuclo-protein.Haemaglutinates goose erythrocytes.Grow in hamster kidney and chick embryo cell tissue cultures with eosinophilic cytoplasmic inclusions but usually without CPE.Pathogenic for mice and other laoratory animals.

Rabies:

DiagnosisVaccinationVaccine fisrt developed by Pasteur in 1885Post-exposure- wound care; combined passive and active immunisation.Semple vaccine

Protozoal Zoonoses

Toxoplasmosis

Babesiosis

Leishmaniasis

Trypasmosomiasis

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