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To examine the susceptibility of pigs for elaphostrongylosis, six 3.5-month-old Vietnam pigs were infected with doses of from 500 to 10000 invasive larvae of E. cervi. In all infected pigs any clinical symptoms of infection were observed. After one month post infection a necropsy of the pig infected with 5000 larvae was conducted. On the surface of the liver itself were found 6 white nodules from 2 to 6 mm in diameter. Third stage larvae of E. cervi were found in enlarged mesenteric lymph nodes. Most of them were dead, but after isolation some were still alive. The rest of the pigs infected with doses of 3000, 2000, 1000, 500 and 10000 larvae, were necropsied successively after 2, 3, 4, 5 and 6 months post infection. Any pathological changes were observed in their organs. In the pig necropsied 2 months post infection, dead E. cervi larvae or their fragments were found in mesenteric lymph nodes, and in the rest of the pigs, in this same localization, only fragments of dead larvae or detritus after their resorption were found. Histopathological examinations confirmed the presence of parasitic nodules in lymph nodes and in livers in which cross-sections of larvae of this parasite have been seen. Results of the presented investigations indicate that pigs are not susceptible to infection of E. cervi larvae. One can suppose that a similar low susceptibility to the discussed parasitosis occur in other omnivorous animals and also in men.
Three 1 year old sheep were infected per os with 1000, 2000, and 13000 invasive larvae of Elaphostrongylus cervi. Animals did not show any clinical symptoms of invasion. No larvae of this nematode were found in the samples of faeces during the experiment. During post mortem examination of infected sheeps no parasites or their larvae were found in tissues, and no pathological lesions caused by parasites were observed.
Faeces of red deers from Białowieża Forest containing first stage larvae of Elaphostrongylus cervi have been stored during live years in -20°C. After this time 52% of the larvae survived. These larvae were fully alive and in experimentally infected snails Helix pomatia developed to the infectious stage.
In 1995 on the area of deer farm in Kosewo 1302 specimens of terrestrial snails of the following species were collected: Succinea putris (1220), Zonitoides nitidus (58), Zenobiella rubiginosa (20), Arion circumscriptus (4). These snails were examinated by compressor method. Only S. putris were infected by larvae of two species of Protostrongylidae. Larvae were found only in snails collected from red deer stockyards, however, none snail collected in fallow deer stockyards was infected. The highest extensiveness of invasion of snails by Elaphostrongylus cervi larvae was 5%, and the maximal intensity reached 105 larvae. Larvae of Varestrongylus sagittatus occurred occasionaly in 0,4% of snails, with the mean intensity of 3 larvae.
The objective of the study was to establish possibilities of the development of the I stage larvae of E. cervi in fishes and amphibians, and possibilities of paratheny in the organism of these animals. In the alimentary tract of the fishes both the I stage and the invasive (i.e. III stage) larvae can not cross the intestine barrier and undergo digestion. However, in the frag organism the I stage larvae of E. cervi are capable of crossing the wall of the alimentary canal and of going through a part of their development, though not attaining the II stage. The invasive larvae fed to the frogs penetrate under the peritoneum, into the mesenterium and the muscles and there they survive inside cysts. Frogs as parathenic hosts for E. cervi can be dangerous for predators feeding on amphibians. The larvae of E. cervi liberated in their organism can pass through the cerebral phase of their development thus causing neural clinical symptoms.
Single doses (from 300 to 1000 larvi per an animal) of invasive larvae E. cervi Cameron, 1931, obtained from experimentally infected snails Helix pomatia L. were given to 17 guinea pigs and 17 golden hamsters. Clinical nervous symptoms in the form of paresis and paralysis of limbs occurred only in the guinea pigs which were given a dose of 1000 larvi. These animals died in the period from the 75th to 117th day of infection. From their central nervous system single adult males and females of E. cervi were isolated. In the lungs and mesenteries of 2 dead pigs live larvae of E. cervi were found. This fact proves that the guinea pig can fulfil the role of a final and a paratenic host of E. cervi. No clinical symptoms were noticed in any hamster. In hamsters dissected on the 7th day of infection live larvae of E. cervi were found in the mesentery and in the fleshy part of the diaphgram. After 14 days the larvae found both in the mesentery and in the diaphragm were dead and surrounded by cellular infiltration. A strong tissue reaction of the hamster after the administration of E. cervi larvae is responsible for the larvae destruction and resorption.
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