Strigea robusta causes polydactyly and severe forms of Rostand's anomaly P in water frogs.

BACKGROUND: Cases of polydactyly in natural populations of amphibians have attracted great interest from biologists. At the end of the 1940s, the French biologist Jean Rostand discovered a polymorphic syndrome in some water frog (Anura: Pelophylax) populations that included polydactyly and some severe morphological anomalies (he called it 'anomaly P'). The cause of this anomaly remains unknown for 70 years. In a previous study, we obtained anomaly P in the laboratory in tadpoles of water frogs that developed together with molluscs Planorbarius corneus (Mollusca: Gastropoda) collected in the field. We thus proposed the 'trematode hypothesis', according to which the infectious agent responsible for anomaly P is a trematode species. METHODS: Metacercariae from tadpoles with anomaly P were identified using ITS2 gene sequencing as Strigea robusta (Trematoda: Strigeidae). To verify teratogenic features of the species, cercariae of S. robusta were tested for the possibility to cause anomalies. Identification of cercariae species was made using morphological and molecular methods (sequencing of ITS2 and 28S rRNA). The tadpoles were exposed to parasites at four doses of cercariae (control, low, medium and high) and divided into two groups: "early" (at 25-27 Gosner stages) and "late" (at 29-34 Gosner stages) exposure. RESULTS: A total of 58 (72.5%) tadpoles survived until metamorphosis under the dose-dependent experiment with the trematode S. robusta. Differences in the survival rates were observed between the exposed and unexposed tadpoles both in the group of "early" tadpoles and "late" tadpoles. The exposure of tadpoles to the cercariae of S. robusta induced anomaly P in 82% of surviving tadpoles. The severe forms developed only in "early" stages under all doses of cercariae exposure. Polydactyly predominantly developed in the "late" stages; under a light exposure dose, polydactyly also developed in "early" tadpoles. Laboratory-hatched tadpoles reared together with infected snails had different rates of survival and complexity of deformations associated with the period of coexistence. CONCLUSIONS: The experiments with direct cercariae exposure provide compelling evidence that S. robusta leads to anomaly P in tadpoles of water frogs. The manifestation of anomaly P turned out to be dependent on the stage of development, cercariae dose, and the location of the cysts.

Distribution of Alaria spp. mesocercariae in waterfrogs.

The distribution of Alaria-spp.-mesocercariae within the host is relevant for the examination via Alaria spp. mesocercariae migration technique (AMT) regarding predilection sites and may indicate an interaction between parasite and host. Naturally Alaria-exposed frogs of Pelophylax species (n = 13) were examined for systemic distribution and localization-specific parasite density of Alaria spp. mesocercariae. The frogs were necropsied and their body was divided into the following localizations: inner organs, head, torso, forelimbs, and hind limbs. The localizations were analyzed individually and in toto using Alaria spp. mesocercariae migration technique. Our results showed neither statistical differences concerning the number of mesocercariae in the different localizations nor in respect of the rate of positive localizations. Therefore, an accumulation in a particular predilection site seems unlikely. Further research on a representative sample is necessary before final conclusions can be drawn.

Papillomatous pastern dermatitis with spirochetes and Pelodera strongyloides in a Tennessee Walking Horse.

Papillomatous digital dermatitis is a common disease in cattle. The pastern dermatitis observed in a horse shared many of the gross characteristics of papillomatous digital dermatitis in cattle. Lesions included a mixture of proliferative and erosive changes, with a verrucose appearance in some areas. Microscopic similarities included pseudoepitheliomatous and papillomatous epidermal hyperplasia with hyperkeratosis, spongiosis of the epidermis, and intraepidermal spirochetes. The horse was also concurrently infected with Pelodera strongyloides. Papillomatous digital dermatitis in cattle is associated with poor husbandry practices. The environment of the affected horse was heavily contaminated with urine, manure, and other organic debris. Verrucous pododermatitis of horses may be the same as or similar to bovine papillomatous digital dermatitis, and these conditions have similar etiologies.

Screening for infection of Trichinella in red fox (Vulpes vulpes) in Denmark.

A total of 6141 foxes (Vulpes vulpes) were examined for infection with Trichinella. The foxes were killed in Denmark during the hunting season 1995-1996 and 1997-1998; 3133 and 3008, respectively. Foxes included in the investigation came from throughout the country with the exception of the island of Bornholm. The right foreleg from each fox was submitted for investigation. The legs were stored at -20 degrees C for 3-10 months prior to examination. Following thawing, muscle tissue (10 g) from each leg was examined by trichinoscopy and by a pepsin-HCl digestion technique. In 1995-1996, three foxes were found positive corresponding to a prevalence of 0.001. Each of the infected foxes harboured an extremely low infection, i.e. about one larva per 10 g muscle tissue. It was not possible to obtain sufficient larval material for species identification. All three foxes were shot in the vicinity of a small village in the north-western part of Denmark. In 1997-1998 no Trichinella cases were found. The results, compared with previous studies, indicate that the prevalence of infection of Trichinella sp. among wild living foxes in Denmark is very low. This is further supported by the fact, that no infection of Trichinella sp. has been found in slaughtered pigs in Denmark for more than 65 years, which suggests that the infection pressure is very low. Considering the facts above we conclude that the risk of Trichinella infections is negligible in intensive indoor pig production units in Denmark whereas high local prevalence of Trichinella infections in the wildlife might constitute a serious risk for the expanding outdoor pig production.

Sites of attachment of Karoo paralysis ticks (Ixodes rubicundus) on three cattle breeds.

The sites of attachment of female Karoo paralysis ticks (Ixodes rubicundus) were determined on Friesian, Bonsmara and Nguni cattle in the south-western Orange Free State. The largest proportion of the ticks (> 30%) attached to the forelegs and shoulders of the cattle. Contrary to the findings on small stock, no significant differences in the preferred sites of attachment were evident between the breeds of cattle.

Recovery, distribution, and development of Acanthocheilonema viteae third- and early fourth-stage larvae in adult jirds.

Living third- and fourth-stage larvae (L3 and L4) of Acanthocheilonema viteae were recovered quantitatively from adult Meriones unguiculatus within the first 10 days after subcutaneous inoculation of 60 arthropod-derived larvae (mL3). The average recovery of the inoculated larvae was about one third (28.5%), and the majority (87.7%) were found in muscular tissues. Seventy-two hours after inoculation, larvae could be isolated from all body locations, although the majority still was found near the site of inoculation. Morphological and biometrical data indicated that, at least until molting, the development of the larval population was not synchronous, with molting occurring over a period of 48 hr on days 7 and 8 postinoculation. The stomatal rings of postinvasive L3's and L4's were distinguishable structurally and could be used as stage-specific determinants. Immediately after infection, L3's showed a linear growth in diameter; rapid longitudinal growth started after the molt, leading to a doubling in the length of L4's within 4 days. The time course of shedding was reconstructed in detail using isolated L3/L4 intermediates.

The quantification of viable Leishmania enriettii from infected guinea-pig tissues.

Results are presented demonstrating that in vitro cultivation of Leishmania enrietti can be used to determine the level of viability in suspensions of L. enrietti used for infection and also to quantify the number of viable organisms in infected tissues.

The kinetics and quality of acquired resistance in self-healing and metastatic leishmaniasis.

Quantitative methods for enumerating viable L. enriettii in tissues have been used to determine the course of cutaneous leishmaniasis in guinea-pigs. The development and kinetics of acquired resistance have been evaluated in self-healing and chronic metastatic forms of the disease. It is revealed that 3 weeks after a primary local infection, a standard challenge infection is totally eliminated within 7 days. This resistance is as strong in animals with a current infection as it is in those that have fully recovered from such an infection. Animals developing metastatic disease also develop resistance to the standard challenge. This is initially as strong as in animals with only localized disease, but wanes with the progression of the infection. Although the quality of resistance becomes poorer in animals with metastatic infection, it is not lost completely. The relationship between acquired resistance and the resolution of the primary infection is discussed.