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Localization, length and reproduction in single- and multiple-worm infections of Echinostoma revolutum (Trematoda) in the chick.

Mono-metacercarial infections of Echinostoma revolutum in the domestic chick yielded 14- or 15-day-old worms that produced viable eggs, indicating that this species can self-fertilize under conditions which preclude cross-fertilization. In multiple infection studies, chicks were fed either 5 or 10 cysts and each infected chick contained 2-7 worms at necropsy 14 or 15 days later. Worms from multiple infections were mainly paired or clustered and they tended to locate more posteriorly in the intestine than single worms. Length measurements of single and multiple worms were similar. Both the number of eggs and the percentage of hatched eggs were considerably greater in multiple than in single infections.

Animals↗

Responses in milk production to control of gastrointestinal nematode and paramphistome parasites in dairy cattle.

OBJECTIVE: To determine the effect of treating naturally acquired gastrointestinal nematode and paramphistome infections on milk production in dairy cattle. DESIGN: A field trial. ANIMALS: One thousand two hundred and thirty nine dairy cows. PROCEDURE: Cows were either not treated or treated with 4.5 mg/kg oxfendazole, 16.6 mg/kg oxyclozanide or 4.5 mg/kg oxfendazole and 16.6 mg/kg oxyclozanide in March, May and August. RESULTS: A significant increase in milk production, averaging 0.4 L (SE 0.2) per day, was seen when dairy cows infected with gastrointestinal nematodes and paramphistomes were treated with oxfendazole or oxfendazole and oxyclozanide in March, May and August. Cows treated with oxyclozanide alone at these times produced no more milk than untreated cows. Faecal egg counts confirmed that oxyclozanide treatment reduced paramphistome populations and oxfendazole treatment reduced nematode populations in cows over the 7-month monitoring period. CONCLUSION: When dairy cows infested with gastrointestinal nematodes and paramphistomes were treated with oxfendazole alone or oxfendazole and oxyclozanide in March, May and August milk production increased.

Animals↗

On the distribution and abundance of eel parasites in Nova Scotia: local versus regional patterns.

Site-to-site variation in macroparasite species distribution and richness was observed in eels (Anguilla rostrata) among 7 sites in the Timber Lake drainage system, Nova Scotia. There was a positive relationship between maximum local species distribution, as measured by maximum prevalence at a site, and regional distribution, as measured by the number of sites in which a parasite was found within the watershed and among 28 sites across Nova Scotia. Species richness increased with spatial scale. However, the species richness of host-specific parasites approached a maximum at the spatial scale of the watershed, whereas that of generalist parasites continued to increase with increasing scale. The near-peak in species richness of eel specialists at the watershed level suggests that in a functional sense for these parasites it is the spatial scale of the watershed that serves as a species pool from which local species richness is derived.

Acanthocephala↗

Heterologous immunity against Schistosoma mansoni in mice by administration of Heterobilharzia americana.

Three groups of Swiss albino mice were exposed to cercariae of Heterobilharzia americana a mammalian schistosome in Southern United States. they were challenged at different intervals with cercariae of a Puerto Rican strain of Schistosoma mansoni, and a fourth group (control for the first two groups) was exposed only to S. mansoni. With a patent infection (two months) of H. americana there was a noticeable reduction of the worm recovery rates of S. mansoni and its eggs deposited in the tissues. In the two other groups exposed simultaneously or at a 3-week interval, there was no significant reduction in the recovery rates of adult S. mansoni and the number of eggs exceeded in some cases that noted for the control group. Thus a patent infection with H. americana is necessary to confer immunity against a challenge infection with S. mansoni.

Animals↗

The laboratory maintenance of Sanguinicola inermis Plehn, 1905 (Digenea: Sanguinicolidae).

Methodology is described for the laboratory maintenance of the life-cycle of Sanguinicola inermis, using common carp (Cyprinus carpio) as the definitive host and Lymnaea peregra as the intermediate host. Lymnaea auricularia was also infected but is not considered to be a suitable laboratory host. Tench (Tinca tinca) were susceptible to infection at high cercarial doses but subsequent infection rates were low. Goldfish (Carassius auratus) and Lymnaea stagnalis were refractory to laboratory infection.

Animals↗

Effect of temperature on the infectivity of metacercariae of Zygocotyle lunata (Digenea: Paramphistomidae).

As a test of the energy limitation hypothesis (ELH), we predicted that temperature would have a significant influence on the infectivity of metacercariae of the digenetic trematode Zygocotyle lunata. Snails infected with Z. lunata were collected from ponds near Crawfordsville, Indiana, isolated at room temperature, and examined for the release of cercariae. Newly encysted metacercariae were collected and incubated 1-30 days at 1 of 5 temperatures (0, 3, 25, 31, 37 C). Twenty-five cysts were fed to each of 5 or 10 mice per treatment group (temperature). At 17 days postinfection, mice were killed and worms were recovered; data were collected on levels of infection in each group and the total body area of each worm. No worms were found in mice fed cysts that had been held at 0 C or 37 C (after 30 days). There were no differences in prevalence, infectivity, or mean intensity among the 3, 25, and 31 C treatments. Infectivity of metacercariae incubated at 37 C for 1 day was significantly greater than in all other treatments, while infectivity of metacercariae in the 37 C/15-day treatment was significantly lower than in all others. Mean body area of worms at 37 C/15 days was significantly greater than at other temperatures, suggesting density-dependent increases in growth. These results, particularly those from the 37 C treatments, are consistent with the ELH; infectivity was lower at high temperatures or when incubated for more time at 1 temperature (fewer energy reserves). It is suggested that microhabitat conditions experienced by metacercariae of Z. lunata could contribute to longer larval life, thus influencing this parasite's temporal dispersal.

Animals↗