[Spontaneous Cryptosporidium infection in weaned rabbits]

The first occurrence of Cryptosporidium parvum Tyzzer, 1912 in broiler rabbits in the Czech Republic is reported. The protozoon was determined on the basis of morphometrical parameters of oocysts and of localization of endogenous developmental stages. The dynamics of natural Cryptosporidium infection was studied in a group of 72 young rabbits after weaning (their age ranging from 23-33 to 82-92 days) obtained from six large flocks and used in a feeding experiment. C. parvum was found in rabbits from four farms (Tab. I). Animals under observation were divided into 9 subgroups according to the genotype (Hyla 2000, California White, crosses of New Zealand x California, New Zealand White, Cunistar and Zika) as well as according to the farm of origin. The animals were housed in 28 cages under the conditions of two-floor cage technology. The upper floor consisted of cages housing three head, the lower floor two head each. The animals were fed ad libitum with commercial feed mixture (till the average age of 64.days supplemented with Robenidin as coccidiostat). During the first 10 days of observation pooled samples of droppings from each cage were examinated by flotation-centrifugation method according to Breza (1957) and Pavlásek (1991) in the intervals of three to four days, later one-week intervals. Post mortem scrapings from mucous epithelium taken from young rabbits were examinated (to reveal endogenous developmental stages of C. parvum) together with digesta (to detect oocysts of the protozoon) taken from the full length of the small intestine using method of native preparations and Giemsa stain. In one 37-day dead animal the small and large intestines were examined histologically. The maximum number of young rabbits infected with C. parvum were 30-40 and 33-43 days old (Fig. 1). In animals of this age category the oocysts of the protozoon were found in pooled samples in 11 and 12 cages (39.3 and 42.9%) from totally 28 cages under study. In rabbits of more than 50 days of age the occurrence of infection was significantly decreased (3.7%). During the experiment seven rabbits (9.7%) died; six of them (8.3%) at the age of 30-40 days. All these naturally infected and dead animals represented cases of monoinfection with C. parvum. The major clinical signs were typical diarrhoea lasting 3-5 days, inappetency, apathia, lethargy, prominent signs of exhaustion followed by dehydration of the organism. Atrophy of villi of the ileum in one of young rabbits was found histologically. Table II presents concrete data on significantly lower body weights (the decrease being 7-61.5%) as compared with rabbits of the same age not infected with cryptosporidia. It was not possible to evaluate objectively the differences in susceptibility to C. parvum infection between the individual genotypes of rabbits. As was found in the course of our further studies (unpublished data) a possible source of infection of young rabbits can be represented by their mothers in which oocysts are excreted sporadically shortly before parturition and during several days after it. Cryptosporidium infection (cryptosporidiosis) in flocks of broiler rabbits is taken as a new protozoal disease in the Czech Republic and C. parvum as one of possible agents in cases of disorders of digestive tract, namely in rabbits after weaning.

The efficacy of ivermectin in treating rabbits experimentally infected with Eimeria as indicated parasitologically and histologically

Ivermectin (Ivomec) was used as coccidiocidal drug against Eimeria in experimentally infected rabbits as indicated parasitologically & histologically. Twenty Bosskat rabbits, were divided in to 5 groups, 3 groups were inoculated with 1000 sporulated oocysts and the other 2 groups were kept as negative controls with and without Ivermectin administration. Ivermectin (1:10) was injected subcutaneously in a dose of 0.5 ml in animals of groups 1,2 & 3. The treatment of group (1) was on the 4th day A.I. and on the 4th day and 7th day A.I.in group (2). The treated animals with one or two doses showed mild coccidiosis with very few number of oocysts deposition & rapid intestinal regeneration with degenerated Eimeria developmental stages, especially the asexual ones.

[Clinical and etiological aspects of goat ear mite infestations in Tuscany]

Parasitic otitis associated with Psoroptes sp. mites was diagnosed for the first time in two flocks of goats located in Tuscany, Italy. Some animals presented clinical signs of ear mite infection, but the parasites were also isolated from the ears of two clinically silent goats. A morphometric study was conducted to establish whether there are significant morphological differences between mites collected from the ears of goats and Psoroptes cuniculi collected from the ears of rabbits. Three rabbits were experimentally infected with mites isolated from the auditory canal of goats, while nine goats were infected with mites isolated from rabbits. After three to five months all rabbits and five of the nine goats contained reproducing mite populations in their ears; also the morphometric analysis revealed no difference between rabbit and goat ear mites. It follows that Psoroptes cuniculi represents the etiologic agent of parasitic otitis in both these two animal species.

Eimeria magna Pérard, 1925: study of the endogenous development of parental and precocious strains

The endogenous development of a parental strain of E. magna and its deriving precocious line was studied after inoculation of coccidia-free rabbits with oocysts or sporocysts directly into the duodenum and using electron microscopy. Four meront generations could be observed mainly in the jejunum and ileum for the parent strain. The first merogony began 24 h post-inoculation (h p.i.). and meronts were matured about 48 h p.i. The second and the third generation were complete at 66 and 84 h p.i. respectively. Thus, each generation needs approximately 16-20 h for maturation. The fourth generation appeared 102 h p.i. and the young gamonts were present 120 h p.i. As in the other rabbit Eimeria, two types of meronts were described: A and B. The morphology of all endogenous stages of the precocious line was similar but refractile bodies were absent in the first generation merozoites and the fourth generation meront was lacking.

Effect of anti-thymocyte serum on acquisition of resistance to infestation by Rhipicephalus appendiculatus larvae in rabbits

Administration of specific goat anti-thymocyte serum (ATS) to rabbits, prior to a primary infestation by Rhipicephalus appendiculatus larvae, blocked the acquisition of resistance significantly only in the third infestation. The larvae which fed on these rabbits had higher engorgement masses than did those feeding on untreated control rabbits. Also, a higher percentage (92%) of larval ticks fed on these animals than on the controls (88%). ATS also induced a leucopenia due to a lymphopenia in the treated rabbits. It was concluded that a T-cell-dependent component might be involved in acquired resistance to infestation by R. appendiculatus.

Generalized encephalitozoonosis in a Jersey wooly rabbit

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A new approach for the identification and the diagnosis of Eimeria media parasite of the rabbit

In this work, we described a new approach for the isolation of a species-specific probe for the Eimeria media parasite of the rabbit based on the use of the random amplified polymorphic DNA (RAPD) technique. A specific fragment of 800 bp of the studied species was isolated after RAPD and then cloned and DIG-radiolabeled. After dot-blotting, we observed that this probe was specific for E. media. Sequencing of the 3' and 5' ends of this probe enabled the determination of two primers that could be used in a PCR reaction. The amplified product of 750 bp was specific E. media. The use of these primers and of our probe allowed the detection of a very small number of oocysts. With a new protocol of DNA purification, 10 purified oocysts were detected by PCR. The efficiency of the amplification was not changed when two species were mixed. The threshold of detection of oocysts in fecal matter was equal to 30.

Rubidium in female Culicoides variipennis sonorensis (Diptera: Ceratopogonidae) after engorgement on a rubidium-treated host

A rabbit given an intraperitoneal injection of 500 mg/kg of rubidium chloride retained elevated blood levels of Rb+ for at least 30 d with no overt effects. All Culicoides variipennis sonorensis (Wirth & Jones) females that fed on the rabbit 1, 4, 7, and 14 d after injection were marked with Rb+ when engorged (day 1), and 95% were marked when gravid (day 3). At 7 d, 79% of flies were marked, and 16% exhibited elevated levels after 14 d. Eggs laid 3-4 d after feeding contained elevated Rb+ levels, and the rapid decline in Rb+ content in females was associated with metabolism of the blood meal and oviposition.

Development of Babesia gibsoni in the salivary glands of the larval tick, Rhipicephalus sanguineus

The development of Babesia gibsoni in the salivary glands of larval Rhipicephalus sanguineus ticks was morphologically studied for 4 days of feeding of tick on rabbits. Babesia gibsoni showed two forms (sporont and sporozoite) in the budding process. Sporozoites were formed in the acinar cells of salivary glands and released from the hollow cytoplasmic area of these cells by day 4 of feeding. The morphology of B. gibsoni in the salivary glands of R. sanguineus shows a close similarity to those of B. gibsoni in Haemaphysalis longicornis.

Cerebral larva migrans caused by Baylisascaris sp in pet rabbits

Cerebral larva migrans was diagnosed histologically in 4 pet rabbits that developed progressive neurologic disease. Larvae of Baylisascaris sp were isolated from brain tissues in 2 rabbits. The clinical syndrome of progressive torticollis and ataxia manifested by these rabbits is commonly associated with otitis and labyrinthitis attributable to bacterial infection; however, the middle ears were normal on radiographic and postmortem examinations. The severe encephalopathy that developed in these rabbits was indicative that just a few Baylisascaris larvae may cause extensive brain injury. During the summer, all of the affected rabbits were maintained outdoors in suburban areas, where raccoons, the final host of B procyonis, are commonly observed. Raccoon feces containing B procyonis eggs constitute a health risk for rabbits, as well as for human beings.

Acaricidal agents of natural origin against Psoroptes cuniculi

Lavandula angustifolia Miller essential oil and some of its main constituents, i.e. linalool, linalyl acetate, and camphor were tested in vitro for their bioactivities against Psoroptes cuniculi (Delafond, 1859), mite of the rabbit. The essential oil and linalool were found to have very powerful miticidal activities.

Effects of human recombinant interleukin-2 on resistance, and on the humoral and cellular response of rabbits infested with adult Ixodes ricinus ticks

Rabbits were treated with subcutaneous injections of ten doses of 5 x 10(3) units of human recombinant interleukin-2 (IL-2) during a first infestation with five adult pairs Ixodes ricinus per rabbit, while untreated controls were infested by either five (direct control) or 25 pairs (resistant control) per rabbit. During the second infestation with 25 pairs per rabbit in each group, rabbits treated with IL-2 became more resistant than the rabbits in the two untreated control groups. Stronger resistance was manifested by lower engorgement and egg laying weights, and by smaller numbers of normally fed or ovipositioning ticks. IL-2 treatment had no significant effects on the rabbit anti-tick antibody production and the lymphocyte proliferation to a salivary gland extract (SGE). By contrast, the highest cutaneous responses to SGE were observed in the IL-2 treated group. IL-2 may increase rabbit cell-mediated immunity, and stimulate an increase in the production of memory cells during the induction phase of the immune response (first infestation), allowing the development of a strong resistance in lightly infested rabbits.

Histopathology of the lungs of rabbits experimentally infected with Dirofilaria immitis

The lungs of rabbits experimentally infected with Dirofilaria immitis were examined histopathologically, to compare the changes with those seen in human pulmonary dirofilariasis. Eight rabbits were infected subcutaneously with two to eight immature worms to induce pulmonary dirofilariasis. Obstructive changes, similar to those reported in human pulmonary dirofilariasis, were observed in the blood vessels surrounding the worms. A form of arteritis, similar to occlusive arteritis, and periarteritis were also observed in the lungs of the rabbits. These results suggest that experimentally induced dirofilariasis in the rabbit is a useful animal model for human pulmonary dirofilariasis.

Failure of immunization with trypanosome endocytotic vesicle membrane proteins to provide nonvariant immunoprotection against Trypanosoma brucei

Purified trypanosome endocytotic vesicles were subjected to Triton X-114 phase separation to obtain a fraction enriched in putative parasite receptors for adsorptive endocytosis. Rabbits immunized with this material produced antibodies that recognized many parasite proteins, including nonvarying epitopes on the parasite's endocytotic surface, the flagellar pocket membrane, as well as on membranes of endosomes and lysosome-like structures. These antibodies were unable to stimulate in vitro complement-mediated lysis of trypanosomes, and in an in vitro test of parasite growth inhibition they actually marginally enhanced parasite proliferation. No effect was observed on the parasite prepatent period or parasitemia in mice injected with antibody purified from the rabbit antisera, but their survival with the infection was significantly shortened. Finally, little difference was detected in parasitologic or hematologic parameters between immunized and control rabbits upon challenge with T. brucei infection.

Dynamics of host blood effects in Glossina morsitans sspp. infected with Trypanosoma congolense and T. brucei

The pattern of infection in Glossina morsitans morsitans and G. m. centralis membrane-fed on eland, buffalo or goat blood mixed with Trypanosoma congolense or T. brucei was studied from day 1 to day 10. Tsetse were initially permissive vectors, with most flies harbouring infections of 10(4)-10(5) parasites on day 3. However, after a second blood meal on day 3, flies cleared many infections, with G. m. morsitans clearing more infections than G.m. centralis. Infective feeds of goat blood consistently increased final infection rates by limiting the number of infections lost between days 3 and 6. In further experiments with G. m. morsitans only, this effect was replicated by feeding flies on erythrocytes but not on serum. These results suggest that compounds from some mammalian erythrocytes match the target specificity of G. m. morsitans midgut lectins and, hence, have a protective effect on trypanosome establishment in the fly.

Histopathology of the small intestinal mucosa in Nematodirus spathiger infection in rabbits

Rabbits were experimentally infected with two levels (5000 and 17,000) infective larvae of Nematodirus spathiger. Histological (villus length, mucosa to serosa ratio, crypt surface) and biochemical (protein content, alkaline phosphatase and leucine aminopeptidase activities) measurements relating to the small intestinal mucosa were examined along the entire length of the organ. In the proximal intestine, the presence of worms was associated with villus abrasion, increased crypt surface and decreased alkaline phosphatase and leucine aminopeptidase activities. Conversely, beyond the main site of infection in the distal small intestine, some signs of hypertrophied villi and crypts were noted without any changes in enzyme activities. These distal variations were similar to those previously described in experimental Trichostrongylus colubriformis infections of rabbits. These results tend to confirm the use of the rabbit as an experimental model to study Nematodirus infection. They also suggest that the distal adaptive process in the nematode-parasitized small intestine could occur independently of the worm species.

Contrasting effects of sera from rabbits and cattle infested with ticks on the in vitro feeding performance of the tick Rhipicephalus appendiculatus

The in vitro feeding activity of partially engorged Rhipicephalus appendiculatus (Neumann) (Acari: Ixodidae) females fed on sera from uninfested hosts was compared to that of ticks fed serum of hosts which had previously been infested with ticks. Although ticks fed best on sera from bovid hosts which had no prior exposure to this ectoparasite, two infestations of a bovid had no significant effect on the acceptability of its serum. In contrast, ticks fed sera from rabbits which had twice been infested with ticks gained significantly less weight than those fed serum obtained from the same animals before the infestations. Clearly there is a difference between natural host resistance and that of laboratory animals.

Changes in immunity to Ixodes ricinus by rabbits infested at different levels

Two groups of rabbits were infested twice with different numbers of Ixodes ricinus adults: one group (high infestation) with twenty-five females and twenty-five males and the other group (low infestation) with five pairs. A third infestation was performed in both groups with fifteen adult pairs. Tick biology was monitored for resistance effects. At the second infestation, the feeding and the egg production were more perturbed in ticks fed on high infestation rabbits. The embryogenesis was only affected in ticks from high infestation rabbits. At the third infestation, resistance was increased only in low infestation rabbits, which became more resistant than high infestation rabbits. The blastogenic response of peripheral blood lymphocytes and antibody production against ticks were assessed. A salivary gland extract and an integumental antigen from I. ricinus adult females were able to initiate lymphocyte proliferation. The response was significantly higher in high infestation rabbits, especially at the end of the second infestation, and higher in low infestation rabbits during the third infestation. Non-specific proliferation with concanavalin A was temporarily decreased in both rabbits groups during the first and the second infestations. Specific antibody response to salivary and integument antigens were always the highest in high infestation rabbits. The involvement of tick-induced immunosuppression is discussed.

Distribution of antigens of Fasciola gigantica at various stages of development

An indirect immunofluorescent antibody test on the serum of a Fasciola gigantica-infected rabbit, showed specific fluorescence on the tegumental surface of miracidia, sporocysts, rediae, cercariae, metacercariae and juvenile worms aged between one and seven weeks. The same reaction occurred in the gut cells of cercariae and metacercariae and in the gut caeca of juveniles in the liver. The results of the absorption test indicated that stage-specific antigen(s) in metacercariae and seven-week-old worms existed mainly in the gut cells and the gut caeca, respectively. The precipitating antibody reacting to metacercariae antigens occurred at a very early stage of infection, but the titre dropped much earlier than that against the juvenile antigen.

Eimeria sp. from the rabbit (Oryctolagus cuniculus): pathogenicity and immunogenicity of Eimeria intestinalis

The pathogenicity and immunogenicity of Eimeria intestinalis was evaluated in SPF rabbits. The animals were given immunizing doses of 6, 6 x 10(2), 6 x 10(3), and 6 x 10(4) sporulated oocysts and were challenged with 3 x 10(3) oocysts. The criteria analysed were the daily weight gain and the oocyst output. This study showed that E. intestinalis had strong immunogenicity, as the inoculation of 6 oocysts was sufficient to minimize the clinical expression of the disease following the challenge and to reduce the oocyst output by about 60%. The immunity towards the excretion of oocysts and the illness was absolute in animals inoculated with 600 or more oocysts. Moreover, this protection seemed to be efficient at least 8 weeks after the challenge. The present results also confirm the pathogenicity of E. intestinalis, although the occurrence of diarrhoea may be irregular, and emphasize the fact that the capacity of this Eimeria for multiplication is not a criterion for clinical diagnosis of the disease.