Domestic Animals

DOMESTIC ANIMALS, from a medical-sanitary point of view, have great significance for humans. Leaving aside the role of D. a. as sources of nutrition, it should be noted that they have other positive aspects of their significance for humans in special relationships. D. a. supply humans with various substances used either as therapeutic agents or in the form of constituens. The latter include lard (adeps suillus=axungia porci), lanolin (obtained from sheep's wool), fats, wax (cera alba, cera flava), etc. For therapeutic purposes, animal blood (sanguis bovinus inspissatus) and normal gastric juice, obtained from an isolated portion of a dog's stomach, are used. Pepsin (Pepsinum) is extracted from the gastric mucosa of sheep, pigs, and calves. Milk sugar is obtained from cow's milk. Various internal secretion organs are used to obtain their active principles either by making extracts (organotherapy) or through chemical extraction of specific components in as pure a form as possible (thyreoidin, parathyreoidin, glandula thymus sice, pulv., pituitrin, preparations from the epiphysis, spermin, oophorin, extract from corpus luteum, preparations from the placenta, adrenaline, insulin, etc.), or by other special methods (Kravkov's method for obtaining secretory products from isolated internal secretion organs by passing Locke's fluid through them). Secretory glands are sometimes also used per se for their transplantation (e.g., testes) surgically to humans. Similar use is made of pieces of bones from D. a. Special preparations include animal charcoal (carbo animalis), bone charcoal (carbo ossium), carbo animalis e sanguine, which also find special application. Catgut is prepared from sheep intestines; silk is twisted from the threads of silkworm cocoons (Bombyx mori), which is widely used in surgery. D. a. are generally used as 'living factories' for producing therapeutic and preventive sera and vaccines. Such is, for example, the role of calves in obtaining smallpox vaccine. Horses are immunized against various toxins of both bacterial and animal nature (antidiphtheric, antitetanic and other sera; monovalent and polyvalent antivenom sera, and many others). The negative significance of D. a. for humans is also multifaceted. Some dangerous diseases of animals are transmitted to humans, such as: rabies, glanders, anthrax, plague, etc.; there are also other diseases common to humans and D. a. (actinomycosis, tetanus). From the milk of goats infected with Micrococcus melitensis (Mediterranean coasts, Malta, southern USSR, etc.), humans get Malta fever, or Mediterranean fever. I. D. a. and internal parasites. Domestic animals play an important role 1) as carriers of parasites common with humans, and 2) as intermediate hosts of parasites that are sources of human infection with parasitic worms. 1. D. a. as carriers of parasites common with humans. In such cases, D. a. a) contaminate the environment with parasites, from which humans can also acquire the corresponding parasites, b) spread the eggs of parasites, which infect intermediate hosts that can become sources of human infection, and c) directly (through contact or consumption) infect humans with parasites. a) Among the protozoa (Protozoa), parasites very similar (if not identical) to the intestinal amoeba (Entamoeba coli, E. dysenteriae, Endolimax nana, Chilomastix mesnili, Balantidium coli) have been found in pigs. The dysentery amoeba is found in naturally infected pigs, which can be temporary reservoirs of these human parasites (Kessel), since their invasion with E. histolytica spontaneously ceases in about six weeks. Pigs are infected with parasitic infusoria (Balantidium coli) pathogenic to humans, while the pigs themselves do not suffer from balantidiasis. A noteworthy fact is that dogs suffer from both cutaneous leishmaniasis (pindling) and visceral leishmaniasis (kala-azar), the parasites of which are indistinguishable from the causative agents of human leishmaniasis (Leishmania donovani, L. tropica). However, the epidemiological relationships between humans and dogs in the spread of these diseases are not yet clear. Among the parasitic worms of humans, species common with domestic animals are: human ascaris (if the majority of parasitologists are correct who consider Ascaris lumbricoides and A. suilla of pigs to be identical), whipworm (Trichocephalus trichiurus, according to Schwarz, identical to the pig whipworm), Strongyloides stercoralis (pig, dog), Necator americanus (pig, dog-rarely), Ankylostoma duodenale (accidentally in pigs). On the other hand, rare parasites of humans can be cat and dog ascarids (Toxascaris, Belascaris). All the above-mentioned hosts of helminths from D. a. can contribute to human infection with these parasites from the external environment. b) Domestic animals are the main hosts of helminths, they spread their eggs with excrement, which promotes the infection of intermediate hosts, which in turn can transmit the parasites to humans; in other cases, humans themselves become intermediate hosts of the helminth, which is the case with respect to the echinococcus and the brain tapeworm. Dogs and cats infect humans with the echinococcus tapeworm. From dogs, humans can similarly become infected with the brain tapeworm (Taenia coenurus). D. a. can infect intermediate (or only first intermediate) hosts of parasitic worms, from which humans then become infected. Such combinations are possible because some parasites specific to D. a. can be parasites of humans. Sheep, cattle, goats, pigs, and horses are infected with the liver fluke (Fasciola hepatica), the intermediate host of which is the small pond snail. There are rare cases of finding F. hepatica in the human liver, who becomes infected with this helminth in the same way as the main host (cattle), by swallowing water with encysted cercariae. The same is true for the intestinal fluke Fasciolopsis buskii, whose main hosts, along with pigs, dogs, and goats, are humans (intermediate host-pond snails Planorbis coenosus and Segmentaria largillierti). The lung fluke, Paragonimus westermani, parasitizes in the lungs of final hosts: pigs, dogs, cats, and humans; among these, D. a. contribute to the infection of the first intermediate hosts in the form of snails of the genus Melania, from which crabs and crayfish become infected, which in turn infect the final hosts (including humans if they eat raw crustaceans). Opisthorchis felineus, the liver fluke of cats (dogs and pigs), is also found in humans if they have eaten raw fish (roach, dace, tench, bream, etc.) with encysted parasites in it. Similar relationships exist for the Chinese fluke, Clonorchis sinensis (human liver, pig, dog, and cat), with the first intermediate host-snails of the genus Bythinia and Melania, and the second intermediate hosts in the form of many carp fish. The unisexual Schistosoma japonicum. parasitizes in the arteries and veins of humans, causing dysentery-like disorders and a form of bilharziasis called the disease of Katayama (Katayama), as well as in pigs, horses, cattle, and dogs. Contact of humans and these animals with bodies of water leads to the contamination of the latter with the eggs of the parasite and the infection of the intermediate host-snails with miracidia that have emerged from the eggs. The invasion of the main hosts occurs through the penetration of cercariae into their skin, which enter the water from infected snails. 50b Among the tapeworms (Cestoda), the cucumber tapeworm [Dipylidium caninum (and probably other species of this genus)] of dogs and cats can be a parasite of humans if the latter swallows the intermediate hosts of the helminth, which are ectoparasites-the dog and cat biting lice (Trichodectes canis, Tr. subrostratus) and fleas (Pulex irritans and Ctenocephalus canis). The broad tapeworm [Diphyllobothrium (=Dibothriocephalus) latum] can parasitize in dogs and cats in the adult stage, in addition to the human intestine. Consequently, these animals can independently maintain the existence of this species of human parasite. Among the nematodes having an intermediate host, through which the parasite passes to the main host, we note the rarely occurring form in humans of Gongylonema pulchrum, which usually lives in the esophageal mucosa of pigs. With the eggs of this parasite, pigs infect intermediate hosts, which are presumably considered to be cockroaches (Blattella germanica) or dung beetles. In their body cavity, the encapsulated larva of the parasite develops. The larvae turn into adult worms if they are swallowed (with the intermediate host) by a pig (resp. by a human). Similar relationships are presented by the life cycle of the giant acanthocephalan, Macracanthorhynchus hirudinaceus [intestine of pigs (humans), body cavity of larvae of rose chafers and May beetles]. Among parasites with an unknown biological cycle, we note the fluke Gastrodiscus hominis (pig, human) and the giant kidney worm, Dioctophyme renale (pig, dog, human-in the renal pelvis).

Man can be the second intermediate host of some parasites of domestic animals. In the intestine of dogs and cats can parasitize the broad tapeworm of Manson, Diphyllobothrium mansoni. From the eggs of this worm, which get into the water, emerges a larva that infects the crustacean Cyclops leuckartii (procercoid stage). If a person swallows such cyclopses with water, then in his body develops the plerocercoid stage, formerly known as Sparganum (also in pigs). Domestic animals can infect a person with various parasites through direct contact; when caring for pigs or inflating with mouth poorly washed raw pig intestines (sausage production, preparation of intestines for export), it is possible to swallow cysts of Balantidium coli and subsequent infection with balantidiasis. The same can also occur in relation to the cysts of the dysentery amoeba (see above). From a dog (and cat) one can become directly infected with echinococcus, because the eggs of this worm, coming out with feces, stick to the fur and skin of the animal. Such parasites as trichina (Trichinella spiralis) do not live in any stage of development in the external environment, but pass from an infected animal to a healthy one when the latter eats the former. 2. Domestic animals are intermediate hosts for some tapeworms of man. The unarmed tapeworm (Taenia saginata) parasitizes in the muscles, tongue, heart and lungs of cattle; the armed tapeworm (Taenia solium) lives in the muscles, heart, brain, eye, kidneys or spleen of domestic pigs. Ox, camel, dog, cat, horse and sheep are also noted as (rare) intermediate hosts of T. solium. When eating meat of intermediate hosts with "live fincae" a person becomes infected with the corresponding tapeworm. For Taenia solium and T. saginata, domestic animals are specific sources of human infection with the tapeworm forms of these worms. II. Domestic animals as suppliers of ectoparasites for man. Some ectoparasites are common to man and various domestic animals. Thus, some ticks of the superfamily Ixodoidea can attach to both; for example, the dog tick - Ixodes ricinus - drinks the blood of cows, dogs and people. Ticks of the genus Ornithodorus - O. papil-lipes (whose role in the transmission of spirochetes of relapsing fever in Turkestan was experimentally proven by I. A. Moskvina in 1927) and O. lahorensis also live at the expense of human and domestic animal blood (sheep, cows, etc.). Mites Dermanyssus gallinae (family Gamasidae) attack chickens and cause in man unbearable itching. Itch mites also pass from domestic animals to man when the latter comes into contact with infected hosts or harness. Such are Sarcoptes scabiei v. equi (from horse), S. scab. v. suis (pig) and others. From dogs and cats to man and back can pass fleas Ctenocephalus canis, Ct. felis, Pulex irritans and others. Finally, from horses a person can get the larva of the 1st phase of Gastrophilus, which, having emerged from the egg glued by the gadfly to the horse's hair, bores into the human epidermis, where it makes its way (see Gastrophilus equi). Probably a similar infection of man from a cow with the larva of Hypoderma is also possible. A number of tissue myiasis of domestic animals and man is caused by larvae of the same species of flies (Wohlfart's fly, etc.).