A survey of Eimeria species in commercially-reared chickens in France during 1994.

In a survey of chicken coccidia in France during 1994, samples of litter were collected from 41 farms. On 31 of these farms, eimerian oocysts were abundant enough to allow monitoring of their numbers in the litter. Peak total oocyst counts on these farms ranged from 16,200 to 1,254,000/g of litter, but no coccidiosis was observed. The chickens reared without anticoccidial agents in their food (poulets biologiques) produced higher and earlier peak oocyst counts in litter than the chickens given medicated food (poulets labels). The oocysts in litter samples from 22 farms (13 poulet biologique, five poulet label, two standard broiler, one breeder and one layer) of the original 41 were identified. Six of the seven eimerian species known to parasitize chickens were found, using combinations of five methods (oocyst morphology, intestinal lesions, enzyme electrophoresis, growth in embryonating eggs and prepatent time). Multispecific infections predominated (95% of 22 farms), up to six species occurring together. Of farms where oocysts were detected, the percentages with each species were: Eimeria acervulina (100%), E. mitis (82%), E. tenella (77%), E. maxima (73%), E. praecox (45%) and E. brunetti (27%). These appear to be the first definite records of E. mitis and E. praecox for France. Although E. necatrix was not found in this survey, it had recently been detected by other workers in France, so that all seven chicken Eimeria species were known to be contemporaneous.

Early migration of immature Fasciola hepatica and associated liver pathology in cattle.

Immature Fasciola hepatica were successfully recovered from the body cavity of cattle from two to 21 days after oral infection. Flukes had penetrated the liver in large numbers by day 7 but there did not appear to be a corresponding reduction in the numbers recovered from the body cavity. Liver pathology showed a typical progressive tissue disruption with a neutrophil and lymphocyte infiltration by day 7 and a marked eosinophil response from day 14. The mesothelium of the liver capsule underwent metaplasia, becoming ultimately highly active and columnar.

Fasciola hepatica: site of resistance to reinfection in cattle.

The effective site of resistance to reinfection of cattle with Fasciola hepatica was examined by recovery of challenge flukes from either the liver or body cavity. Calves infected 18 or 26 weeks previously with F. hepatica showed levels of resistance to reinfection of 56 and 94%, respectively, as assessed by recovery of flukes from the liver 15-16 weeks after challenge. Plasma glutamate dehydrogenase (EC 1.4.1.3; GLDH) enzyme activity estimations revealed only a marginal increase in these latter resistant calves compared with previously naive controls, indicating minimal liver damage as a result of migrating flukes. By comparison, when immature challenge flukes were recovered from the body cavity 4 or 14 days after infection of corresponding previously infected or naive calves, there was no significant difference in numbers. It appears, therefore, that, in cattle, resistance mechanisms are effective against challenge flukes at or soon after penetration of the liver.

Antibody response in cattle, sheep and rats to infection with gamma-irradiated metacercariae of Fasciola hepatica.

Cattle, sheep and rats were infected orally with gamma-irradiated (4 krad) metacercariae of fasciola hepatica, or with normal metacercariae. The antibody response was monitored in each host to metacercarial tegument (T0), juvenile tegument (T1), adult tegument (T2) and gut antigens. The response was examined at weekly intervals for cattle and sheep throughout 15 weeks of infection and four weeks after infection in rats, using an indirect fluorescent antibody labelling technique. It was found that the irradiated metacercariae engendered a normal humoral response to T0, T1 and gut antigens in all three hosts although the antibody levels were somewhat reduced due to an early death or stunting of the flukes. T0 and T1 appeared to be antigenically similar. Antibodies against T2 appeared late in the animals infected with gamma-irradiated metacercariae and the titres attained were considerably lower than in the controls. the T2 antigen stimulus in the animals given gamma-irradiated metacercariae was probably provided by flukes which 'broke through' the developmental barrier imposed by irradiation and which were found alive at autopsy.

In vitro cell adherence to newly excysted Fasciola hepatica: failure to affect their subsequent development in rats.

Newly excysted juvenile liver flukes were maintained in vitro for 24 hours in the presence of normal or immune rat serum alone, or with the addition of rat cells derived from the peritoneal cavity. Serum was changed and fresh cells added every four hours. Cells were seen to adhere to the flukes in the presence of immune serum throughout the period of incubation, and in the absence of cells this serum induced a precipitate around the flukes. Viability of the flukes, as measured by their transfer to the peritoneal cavity of naive rats and recovery from the livers three weeks later, was unaffected by the treatment.

The role of the thymus in the eosinophil response of rats infected with Fasciola hepatica.

The blood eosinophil response of normal and congenitally athymic nude rats was studied following infection with the parasitic trematode Fasciola hepatica. A marked eosinophilia was evident irrespective of the presence or absence of a thymus in the infected rats, suggesting that thymus-dependent mechanisms are not essential for the induction of eosinophilia in the rat.

Hypersensitivity in rats infected with Fasciola hepatica: possible role in protection against a challenge infection.

Rats infected with Fasciola hepatica showed an increase in intestinal mast cells which reached a peak between four and six weeks and fell to control levels by week 14. Following a challenge infection sensitised rats showed evidence of a transitory mild intestinal anaphylactic response. The numbers of intestinal eosinophils, already increased as a result of the primary infection, were rapidly supplemented. In previously uninfected rats the majority of flukes penetrated the mid gut region, but in sensitised rats there was a shift towards the caecal end. Resistance to challenge and a pronounced intestinal eosinophil response were evident in previously infected rats irrespective of the presence or absence of detectable serum reaginic antibody. Systemic anaphylaxis, induced by intravenous fluke antigen administration, occurred whether serum reagins could be detected or not.

The heterologous protection of rats against a challenge with Fasciola hepatica by prior infection with the nematode Nippostrongylus brasiliensis.

Previous infection of rats with nippostrongylus brasiliensis was shown to result in protection against an oral challenge with Fasciola hepatica metacercariae but not against an intraperitoneal challenge with newly excysted juvenile (NEJ) flukes. The timing of the challenge was important and a double infection with the nematode gave more consistent results than a single. Resistance appeared to be associated with a prior induction of intestinal eosinophilia. Sera from these resistant rats, however, failed to induce eosinophil adherence to NEJ flukes in vitro.

The different stages of Fasciola hepatica capable of inducing immunity and the susceptibility of various stages to immunological attack in the sensitised rat.

Intraperitoneal sensitisation of female Piebald Virol Glaxo rats by the migratory immature stages (two-hours-, six-days- and 14-days-old) of the liver fluke Fasciola hepatica protected them from intraperitoneal challenge with living adult flukes three weeks later. Sensitisation with adult fluke antigen and Freund's complete adjuvant had no effect. Flukes attenuated by gamma irradiation (3-8 kiloroentgen), and so prevented from developing beyond the eight to 10 day stage, did not protect against adult challenge. When rats were sensitised orally with metacercariae and challenged with 14-day-old flukes intraperitoneally the challenge flukes were not adversely affected. It is suggested that although 14-day-old flukes can immunise rats adequately, the fact that they are not killed when placed in sensitised rats may be due to the protective effect of tegumental replacement in these flukes before gaining access to, and safety of, the liver site.

The selective adherence of rat eosinophils to newly excysted Fasciola hepatica in vitro.

Eosinophils present in a mixed population of peritoneal cells, derived from either normal or fluke infected rats, selectively adhered to the tegument of newly excysted Fasciola hepatica in vitro in the presence of immune serum. Adherence occurred independently of complement, was not affected by the age of the sensitising infection and could not be induced by artificially raised antisera to dead fluke antigens.

Failure to demonstrate resistance in goats, sheep and cattle to Fasciola hepatica after infection with Cysticercus tenuicollis.

Goats, sheep and cattle given 1000--1500 eggs of Taenia hydatigena and challenged orally 12 weeks later with 400 Fasciola hepatica metacercariae, showed no evidence of resistance. The fluke burdens were not significantly different from those in control animals.

Resistance of the rat to reinfection with Fasciola hepatica and the possible involvement of intestinal eosinophil leucocytes.

Rats infected three weeks previously with 30 Fasciola hepatica cysts were shown to be highly resistant to oral reinfection, as measured by the recovery of immature flukes from the peritoneal cavity 48 h after challenge and confirmed by liver recoveries three weeks after challenge. Eosinophils were prevalent in the lamina propria of the small intestine three weeks after primary infection and increased markedly after challenge.

The establishment and duration of Fasciola hepatica infections in two strains of rats and the development of acquired resistance.

Male and female rats of the inbred Piebald Virol Glaxo ( PVG) and Sprague Dawley (SD) strains were infected with 20 metacercariae of Fasciola hepatica. Three months after infection there was a highly significant difference (P LESS THAN 0-001) in the fluke burden of the two strains. The PVG rats (average 9-4 flukes) were more susceptible than the SD strain (average 2-8 flukes). The PVG males (11-6 flukes) were also found to be significantly more susceptible than the PVG females (average 7-2 flukes) whereas the sex of the SD rats did not affect the fluke burdens significantly. Seven to eight months after infection the PVG rats had eliminated their flukes. These 'self cured' PVG rats were significantly resistant to oral challenge with 20 metacercariae. In marked contrast the SD rats had not eliminated their flukes at the termination of the experiment 12 months after infection.

The microbiological and parasitological colonisation of specified-pathogen-free mice maintained in a conventional animal house.

2 groups of 44 specified-pathogen-free (SPF) mice, caged in groups of 4, were housed at weaning either in isolation in a building housing conventionally-reared animals, or in contact with those animals. 4 mice from each group were examined for microbiological flora and 4 for parasites at intervals for up to 90 days after transfer. Proscribed bacteria were isolated from the "in contact' group after 42 days and endoparasites were observed by 16 days and thereafter. No proscribed bacteria were isolated from the other group, although some endoparasites were observed by 16 days. Proscribed bacteria were shown to be present in the conventionally-reared animals at weaning and ecto- and endoparasites by day 16 and thereafter. It is suggested that it may be possible to maintain SPF animals outside a SPF Unit for short periods of time, and that with great care the animals remain free of proscribed microflora.