Types of Zoonotic Parasites| Microbiology

The following points highlight the top four types of zoonotic parasites. The zoonotic parasites are:- 1. Protozoa 2. Nematodes 3. Trematode and 4. Cestodes.

Zoonotic Parasite # 1. Protozoa:

Cryptosporidium (Parasite of fowl, rodents, cat­tle) is unrecognized cause of self-limited mild gastro­enteritis and diarrhea in man. Leishmania identical to L tropica causes orien­tal sore in dogs of Iraq, Iran, Turkestan, Mumbai, North­ern Africa, L donovaniis transmitted secondarily from dog to sand fly to man in some endemic areas of China, Mediterranean countries and Brazil. Cat, horse and sheep have been reported infected with Leish­mania morphologically similar to L. donovani.

T.gambiense:

There is no proof any of the game animals of Africa act as reservoirs of T. gambiense infection for man, but domestic animals (Cattle, pigs, goats) carry this infection for long periods of time without apparent symptoms.

T. rhodesiense:

The reservoirs of infection of T. rhodesiense for man are believed to be game ani­mals in Africa.

T.cruzi:

In South America, various animals (dogs, cats, armadillos, bats, ferrets, foxes) have been found to be naturally infected with T. cruzi. Dogs and cats may be the common reservoirs of T.cruzi infection in South America.

Entamoeba Histolytica:

Animal reservoirs of E. histolytica include monkeys, dogs and possibly dogs, but these animals at most constitute a minor source of human exposure compared with man himself.

E.coli:

Although monkeys and occasionally the dogs have been found to be naturally infected with Entamoeba morphologically similar to Ecoli, human infection results from the human source.

Isospora Hominis:

Dogs are suspected to be reservoir hosts of I. hominis. Toxoplasma gondii infection may occur in man or in any warm-blooded vertebrate animals (cats). Ap­parent toxoplasmosis is common in reservoir hosts and in man.

Balantidium Coli:

Man is relatively refractory to infection with B. coli of porcine origin. In New Guinea where the pigs are the principal domestic animals, human infections in pig farmers are common to some extent.

Zoonotic Parasite # 2. Nematodes:

Trichinella Spiralis:

Pigs, rats, carnivorous, om­nivorous wild hosts are primarily infected with trichi­nosis, whereas pigs, wild boars, bears, cats, dogs and other mammals which eat flesh become secondarily infected. Polar bears are probably the usual source of human infection in Alaska. Epidemic outbreaks due to consumption of sausage from infected hogs are common.

Strongyloides Stercoralis:

While man is impor­tant host of S. stercoralis dogs and chimpanzees have been found to be naturally infected with strains in­distinguishable from those in man.

Ankylostoma Duodenale:

Man is the only nor­mal definite host of A. duodenale, although a single female worm from a tiger (Kolkata) and hookworms identified as A. duodenale have been reported from the pig, dog and several species of wild animals in captivity. A. ceylanicum, described from the intestine of a civet cat from Ceylon, parasitises to a lesser extent the dog and man.

A. braziliense:

Though first reported from cats and dogs in southern Brazil, it has been incorrectly reported from man in many countries including India and Sri Lanka.

A. caninum is a common parasite of dogs and cats and has been reported once as a parasite of man in Philippine islands.

Necator americanus is a parasite of the small intestine of man (natural host). A hookworm mor­phologically indistinguishable from N. americanus of man have been recovered from several species of simian hosts, rhinoceros, pangolin (Indonesia), rodent (Africa).

Trichostroncylusare commonest parasites in the digestive tract of herbivorous animals throughout the world (Egypt, India – Assam, America).The majority of species occur only as accidental infection of man.

Haemonchus contortus is commonest parasite of domestic sheep throughout the world. Human in­fection is also less common.

Metastrongylus Elongates:

Commonly parasitises the respiratory tract of hogs, less commonly of sheep and cattle. Few human infections are on record. Though Angiostrongylus cantonensis, originally described from the rats, is less commonly reported from human infection.

Syphacia muris and S. Obvelata:

These oxyurids are cosmopolitan in rats and mice, their eggs occur rarely in human feces.

Toxocara canis is a cosmopolitan parasite of dogs. Intestinal infection with the adult worm has been reported from the fox and twice from man, although authenticity of the human infection is questionable.

T. catis is the common ascarid of the domestic cat and some of its wild relatives. Some cases of this infection in man have been recorded.

Gongylonema Pulchrum:

This thread like nema­tode is a cosmopolitan parasite of ruminant and has been diagnosed from pigs, bears, monkeys and occa­sionally from man. It was first recovered as a human parasite in Italy, since then additional infections in man have been reported. Gnathostoma spinigerum has been reported from the domestic cats, wild cat, lion, leopard, mink and the dog in India and in other countries. Human cases are reported from India and countries.

Dipetalonema Perstans:

Man is the important definite host for this species, although primates in Africa and New World monkeys act as reservoir hosts.

Thelazia callipaeda (Oriental eye worm) is spiruroid nematode of the conjunctiva of dog, rabbit and man.

T.californiensis:

In addition to T.callipaeda, many species of this genus have a predilection for the con­junctiva of mammals, birds and many human cases have been reported. Dirofilaria immitis, D. conjunctivae, D. tenuis, D. repens are microfilariae of animals and they may be­come adults in man without producing microfilaria.

Zoonotic Parasite # 3. Trematode:

Schisto somajaponicum. Dogs, cats, rats, mice, field mice, cattle, water buffaloes, pigs, horses, sheep and goats are naturally infected with S. japonicum in many endemic foci.

S. mansoni. Human infection is almost derived from human sources, although monkeys, baboons, gerbil, wild rodents, rats have occasionally been found infected with S. mansoni in endemic areas.

S. hematobium. In addition to man, the usual host, the monkeys, baboons and chimpanzees have been found naturally infected.

S. bovis, common parasite of cattle, sheep, goats, and equines have been reported from baboons. Iso­lated cases of recovery of S. bovis eggs from human urine and stools in South Africa, Southern Rhodesia (Zimbabwe) and Congo lack satisfactory proof. In Italy, this species causes cercarial dermatitis in man. Eggs are longer and much narrower than those of S. haematobium.

S. mattheei is a natural parasite of sheep, goat, cattle, monkeys and rarely man in South Africa, Rhodesia (Zambia and Zimbabwe).The eggs of this worm were found in the human urine and adults were also found associated with those of S. hematobium in two human autopsies. In Rhodesia, over 1 per cent of persons were infected with S. mattheei; eggs are found in stool and urine with equal frequency.

S. nasalis is a common parasite of cattle in India (Pondicherry, Panjarathinam, 1972), but there has been no record of human infection.

S. rhodhaini is the parasite of African wild ro­dents, dogs, cats. Human infection with S. rhodhaini has been reported in Congo.

S. incognitum is the natural parasite of Indian pigs and dogs.The eggs were twice recovered from human feces.

Trichobilharzia ocellata, Schistosoma spindale, animal schistosomes, cause cercarial dermatitis in man.

Gastrodiscoideshominis, common human para­sites in India and other countries, has been found to infect pigs (common reservoir hosts) and monkeys in India.

Fasciola Hepatica:

Reservoir hosts (Primarily sheep) play the important role in the propagation of this infection in Nature and, hence, the human infec­tion occurs. Fasciolopsis buski is a common parasite of man and pig in central and South China and other coun­tries. Dogs are occasionally infected. Other domestic animals, with possible exception of rabbits are prob­ably refractory.

Echinostoma Ilocanum (Garrison’s Fluke):

Rats and dogs are reservoirs of E. ilocanum infection. Hu­man infection is acquired from the consumption of raw snails containing encysted metacercariae.

Echinochasmus Perfoliatus:

This echinostome has also been recovered from pig and fox and a hu­man infection has been reported in Japan.

Plagiorchis muris is a natural parasite of several group of birds at Douglas Lake and has been reported once from man in Japan.

Dicrocoelium dendriticum is a common para­site in the biliary passages of sheep, deer, herbivo­rous and omnivorous mammals. Many genuine hu­man cases have been diagnosed from Europe, Asia and Africa.

Troglotrema Salmincola:

Human infection is in­cidental to that in reservoir hosts (dogs, fox, raccoon, and mink).

Paragonimus Westermani:

The natural definite hosts are man, tiger, cat, civet cat, leopard, panther, fox, wolf, dog, pig.

Opisthorchis felineus:

Man, dog, cat, red, silver, and polar foxes, domestic and wild swine, Norway rat, water rat are infected. The definite hosts acquire infection from consumption of infected raw fish.

Clonorchis Sinensis:

In addition to man, many reservoir hosts (principally the dog, cat) are naturally infected.

Heterophysesheterophyses:

In addition to man, H. heterophyses has been found as natural infection in the cat, dog, fox and other fish-eating mammals in endemic areas.

Metagonimusyokogawai:

Fish-eating mammals and even the pelican are reservoir hosts of the infec­tion.

Zoonotic Parasite # 4. Cestodes:

Diphyllobotrium latum. Man, domestic dog, cat, leopard, mongoose, foxes, seals, sea-lions, bears, minks, domestic pigs have been found infected with D. latum.

Dipylidium caninum. Dogs and cats are avail­able sources of infection for man to whom it is un­common.

Hymenolepis nana fraterna. The variety in ma­rine hosts is infective for man only under exceptional circumstances.

H.diminuta. The tape worm is a common para­site of the rat, mouse, dog (rarely), however, authen­tic human cases have been reported.

Taenia solium. Man is the usual definite host and gets infected by eating inadequately heated pork. Pigs, less frequently sheep, dogs and cats harbour the cysticercus stage of T.solium.

T.saginata. Human infection is acquired by con­sumption of inadequately cooked beef containing the viable cysticercus larvae.

T. taeniaeformis is a normal, parasite of the in­testine of the cat which becomes infected from sat­ing infected rats. A single human infection has been reported.

Multiceps multiceps. Dog, wolf and fox are defi­nite host of this worm. The larval stage is usually found in herbivorous animals (sheep, goats, cattle, horse). Human infection results from the ingestion of eggs passed in dog’s feces.

Multiceps glomeratus is reported from the gerbiland man.

Multiceps serialis is a parasite of dog, wolf, fox and rodents. Human infection is also on record.

Multiceps brauni. This cestode was described from the intestine of dog. Infection with the coenurus (bladder worm) has been recorded in man. In 2 patients the parasite was located in the eye.

Echinococcus granulosus. The dog is the opti­mum definite host, although man, wolf, jackal, fox, domestic cat have been found infected in Nature. Cattle, sheep and pigs are the common reservoirs of the hydatid cyst.

E. multilocularis. Man gets infected sporadically from eggs of E. multilocularis infected fox’s excreta.