GENERAL PARASITOLOGY AND PROTOZOLOGY

PRESENTATION

TOPIC: PARASITIC ZOONOSIS

SUBMITTED TO: DR.MURTAZ UL HASSAN

SUBMITTED BY : AQEEL AHMAD (07-ARID-1690)

BADAR HUSSAIN (07-ARID-1705)

SAHIL JOHN (07-ARID-1721)

MUHAMMAD HAISEM (07-ARID-1722)

ZOONOSIS:

INTRODUCTION:

The World Health Organization defines Zoonoses (Zoonosis, sing.) as "Those diseases and infections which are naturally transmitted between vertebrate animals and man".

CLASSIFICATION:Zoonoses can be classified in many ways:According to the mechanism of transmission Anthropozoonoses: Infections transmitted to man from lower vertebrates (ex: rabies, toxoplasmosis) Zooanthropozoonoses: Infections transmitted from man to animals (ex: diphteria, amebiosis) Amphixenoses: Infections maintained in both man and lower vertebrates, and may be naturally transmitted in either direction (ex: Staphilococcus, mycobacteria)

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According to the life cycle

Direct Zoonoses: Transmitted from infected vertebrate host to a susceptible vertebrate host by direct contact or by a mechanical vector. No developmental change or propagation of the organism occurs during the transmission (ex: Rabies, trichinosis, and brucellosis)

Cyclozoonoses: Requires more than one vertebrate host, but no invertebrate host.  (ex: Echinococcosis, human taeniasis and Pentastoma infections)

Metazoonoses: Agent multiplies, develops, or both in an invertebrate host before transmission to a vertebrate host is possible. (This means that a definite prepatent or incubation period must be completed before transmission.) (ex: Arboviruses, plague, and schistosomiasis)

Saprozoonoses: To transmit these infections a non-animal development site or reservoir is required, such as food plants, soil, or other organic material. (ex: larva migrans and some of the mycotic diseases)

According to the etiology (mostly used)

Bacterial zoonoses: Botulism, tuberculosis Viral zoonoses: Rabies, Hepatit A virus Fungal zoonoses: Aspergillosis, actinomycosis Protosoal zoonoses: Anaplasmosis, babesiosis, malaira Helmintic zoonoses: Trichinosis, echinococosis, taeniasis

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TOXOPLASMOSIS:

Causative agent : Toxoplasma gondii

A coccidium belonging to phylum ApicomplexaToxon = arc; Plastos = form. One stage in the life cycle is arc- shaped. The species name is derived from the host in which the parasites was first described: Ctenodactylus gundi = small African rodent.

HOST: mammals. Especially cats, food animals ,birds and humans. Mode of transmission: ingestion of oocysts shed in feces of infected cats or found in raw meat and milk.

Pathology:

Trachyzoite multiplication results in focal necrosis, the most characteristic lesion of toxoplasmosis. Inflammation usually follows necrosis. Pneumonitis is the predominant lesion in fatal toxoplasmosis in cats and dogs; placental necrosis with white flecks or multiple white, chalky, necrotic nodules and associated abortion predominate in sheep and goats. Histologcially, this necrosis is confined to the cotyledons where individual and small group of tachyzoites are often difficult to recognize among degenerating host cells. Encephalomyelitis is the predominant lesion in sheep. 

Diagnosis:Diagnosis of Toxoplasma is performed at postmortem by identification of organisms in infected tissue. Diagnosis in live animals is aided by serologic tests and in cat by fecal examination.

Prevention and Control:

The following preventative measures apply to all persons, but because toxoplasmosis is most severe in the prenatal period, they should be emphasized for pregnant women and for young children.1. Avoid contamination with oocysts from cat feces by:

a. Feeding cats dry, canned or thorougly cooked food b. Preventing cats from hunting birds and rodents c. Emptying litter boxes daily, before oocysts sporulate d. Wearing gloves or thoroughly washing hands after working in the garden or with soil, and before eating or touching the face e. Covering children’s sandboxes when not in use f. Preventing aerosols in the laboratory during centrifugation of potentially infected biological samples g. Boiling drinking water from streams, ponds, or lakes frequented by cats

2. Avoid ingestion of tissue cysts by cooking meat to over 660 C and washing hands after handling raw meat.

The following preventative measures apply to farms and other animal-rearing facilities. Avoid contamination of feed or water with oocysts in cat feces by:1. Using rodenticides and traps to prevent cats from hunting rodents 2. covering, closing or locking feed-storage facilities to prevent cats from entering and defecating 3. Promptly removing cat feces from building stalls or cages; and flushing, burning, or burying them to destroy oocysts 4. Providing adequate dry, canned, or thoroughly cooked food and separate water to prevent cats from sharing facilities used by other animals.

SARCOCYSTIS :

Causative agent: Sarcosystis suihominis. S. hominis

A coccidium belonging to phylum ApicomplexaHumans may become infected by two species, S.hominis and S.suishominis

HOST: man, cattle and swine

Mode of transmission: ingestion of raw pork or beef; ingestion of feces.Ingestion of raw beef ; ingestion of feces.

LIFE CYCLE:

Pathology

Some species of Sarcocystis are pathogenic to the herbivore intermediate host. Acute lesions characterized by hemorrhage, edema, and necrosis are associated with the maturation of second generation meronts. Macroscopic lesions observed postmortem may include generalized serous atrophy of fat, excessive yellowish fluid in all body cavities, watery blood, petechical hemorrhage in the heart and pericardium, serosa of the gastrointestinal tract and urinary bladder, edema and hemorrhage of lymph nodes, and alternate pale and dark striping or mottling of skeletal muscles. Microscopically, hemorrhage may be seen in all organs, and mononuclear cell infiltration into the perivascular tissues of the hear, skeletal muscles, lung, liver, and kidney may be mild to severe. Regenerative changes are most often associated with the myocardium. Chronic lesions charactgerized by muscle atrophy and myositis are associated with mature saccocysts. Specific macroscopic lesions may not always be seen postmortem. Microscopic lesions may include myositis and myocarditis. Most definitive hosts are clinically unaffected by Sarcocystis infection. 

Diagnosis:

EXAMINATION OF feces

Serologic tests

Meat inspection

CONTROL:Cattle or swine should be prevented from ingesting human feces and humans should avoid eating raw or undercooked meat.