The overwintering of eggs, intramolluscal stages and metacercariae of Fasciola hepatica under the temperatures of a Mediterranean area (Madrid, Spain).

The survival of embryonated and unembryonated eggs, of snails with mature or immature infection and of metacercariae over the winter of a Mediterranean area was analyzed. Embryonated eggs were more resistant than unembryonated eggs to cold weather, leaving a residual contamination which was responsible for earlier spring infection of the snail. Overwintering was similar in snail populations with both mature and immature infections although the lifespan was shorter in the former. Both snail populations survived in the mildest winter but not in the coldest. Only metacercariae from mid autumn were able to overwinter in an significant proportion (45%) but they were non-viable by mid spring. Our results suggest that in very cold winters no risk for grazing animals should be expected in spring.

Coccidial infection in mouflon, Ovis musimon, in central Spain.

From February to September 1993, ten adult female mouflons (Ovis musimon) and their five offspring from central Spain were examined weekly for coccidial infection. All adult mouflons had Eimeria spp. infections with mean (+/- SD) intensity of 1,869 (+/- 1,264) oocysts per gram of feces the day of capture, increasing progressively during the first two months in captivity and later returning to the initial values (1,869 +/- 1,547). The mean (+/- SD) oocyst shedding in young animals was 16,800 (+/- 966) oocysts per gram at 1 mo and 18,796 (+/- 1,220) at 1.5 mo of age and more than 40,000 (40,250 to 52,000) at 3 mo of age; this high intensity was associated with a transient diarrhea. The species involved, in order of frequency, were E. bakuensis (syn. Eimeria ovina), E. ovinoidalis, E. crandallis, E. caprovina, E. parva, E. faurei, E. granulosa and E. intricata, and one more not previously described and recorded as Eimeria sp.. The predominant species for both age groups was E. bakuensis.

Natural infection by gastrointestinal and bronchopulmonary nematodes in mouflons (Ovis musimon) and their response to netobimin treatment.

Gastrointestinal and bronchopulmonary nematode infections and the efficacy of netobimin (Hapasil) were analyzed by way of fecal examination in 10 female mouflons (Ovis musimon), in central Spain, February 1993. Before treatment all 10 mouflons had Trichostrongylus axei, Teladorsagia circumcincta and Marshallagia spp.; sic had Nematodirus spp., two had Trichuris sp., one had Capillaria sp., seven had bronchopulmonary Dictyocaulus filaria and 10 mouflons had protostrongylid lungworms (Muellerius capillaris, Protostrongylus rufescens, Cystocaulus ocreatus or Neostrongylus linearis). Netobimin (7.5 mg/kg) was 100% effective against T. axei, T. circumcincta, Marshallagia spp., and D. filaria infections whereas one animal continued eliminating Nematodirus spp. eggs. The drug also was effective against Capillaria spp. but not against Trichuris spp. or protostrongylid infections.

The overwintering of Fasciola hepatica eggs under semi-arid and temperate Mediterranean climate (Madrid, Spain).

In this experimental work, conducted over two consecutive years (1988 and 1989), we have analyzed the overwintering possibilities of Fasciola hepatica eggs deposited in winter in a semi-arid and temperate Mediterranean area (Madrid, Spain). Eggs did not survive for more than a week in faeces at environmental moisture conditions. In contrast, over a 75% of the eggs maintained in permanently wet faeces survived winter temperatures, showing no high mortality until important thermic increment from June. The success of overwintering was higher in eggs arrested in wet faeces than included in water (55% "versus" 20% of hatching in spring), and it was unrelated to the deposition time (excretion in early or late winter). The hatching period of overwintered eggs started in May, at the same time as those excreted in early spring. Therefore, overwintering of eggs will have an effect on the level but not on the start of the spring contamination with miracidia. The dry winters of this semi-arid area greatly restrict the overwintering eggs contamination to soils next to streams, ponds or irrigation channels.

Seasonal availability of Fasciola hepatica metacercariae in a temperate Mediterranean area (Madrid, Spain).

In this experiment, conducted over a 3-year period (1988-1990), the seasonal availability of Fasciola hepatica metacercariae in a temperate Mediterranean area (Madrid, central Spain) was analysed according to the rhythms of snail infection, the periods of cercarial emission, and the resistance of metacercariae. In this area, snails could be infected from late April to early November. Cercarial emission by spring infection started at the beginning of summer and terminated 3-4 weeks later. Mid-summer temperatures led to the extinction of shedding populations and of the metacercariae emitted by them, but were well tolerated by the snails with undeveloped infections. No aestivation was observed and summer infection led to a progressive shedding wave from August to late December, when it was interrupted. These populations became extinguished in the colder winter of 1988, but overwintered in the mild and belated winter of 1989. Only the snails infected from late summer onwards resumed activity and shed cercariae in spring, from the second half of March to late June. Risk of infection for grazing animals during winter will depend on survival of metacercariae. With a mean mortality of 23% during December and January, and of 38% during the following 2 months, no more than 30% of metacercariae reach the spring alive. Accordingly, risk of infection for grazing animals in spring will depend on overwintering infection of snails. These results indicate that temperature more than humidity could be responsible for different transmission patterns from year to year as winter thermic profiles could be the key for the transmission of fasciolosis during spring.