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Resumen En 26 perros positivos y 20 negativos a microfilarias de Dipetalonema sp. se realizaron examenes hematologicos con el proposito de determinar variaciones en el cuadro leucocitario producidas por el parasito. Entre ambos grupos de perros el hematocrito (VGA), numero de leucocitos totales y el recuento diferencial, tanto en valores absolutos como relativos, no presentaron diferencias significativas. De lo que se desprende que el parasito no produce eosinofilia u otra variacion en los leucocitos sanguineos. Zusammenfassung Blutwerte bei Hunden mit Microfilarienbefall (Dipetalonema sp.) Bei 26 Hunden mit und 20 Hunden ohne Microfilarienbefall durch Dipetalonema sp. wurden vergleichende hamatologische Untersuchungen angestellt. Zwischen beiden Gruppen traten keine signifikanten Unterschiede hinsichtlich Haematokrit-Wert, Gesamtleikozytenzahl und Differentialblutbild auf. Dies bedeutet, das der Parasitenbefall keine Eosinophilie oder sonstige Anderungen im Leukozytenbild verursacht. Summary Haematological Values in Dogs Infected with Microfilaria of Dipetalonema sp. The packed cell volume (PCV), total white blood cell count (WBC) and differential white blood cell count were performed in 26 dogs infected with Dipetalonema sp. and in 20 dogs negative to microfilaria. The results obtained in both groups of dogs did not present a significant difference in all the parameters studied. It is concluded that the parasite does not produce an eosinophilia or other significant change in the leucocyte count.

Summary objective To determine mitogenic and antigen-specific cellular immune responses of two species of rodents, viz. Merionesunguiculatus and Mastomyscoucha to assess the usefulness of the A. viteae/Mastomys model for cellular immune studies in experimental filariasis. methods Lymphocyte blast transformation test (LTT) using spleen cells of normal and A. viteae infected animals. results The proliferative response of gerbils was much higher than that of Mastomys to both ConA and filarial antigens. Cells of both species of rodents did not respond to microfilarial (mf) antigen, however, their mitogenic response differed during infection. Some degree of nonspecific suppression was observed in gerbils during prepatent and patent stages of infection, while Mastomys revealed highest proliferation during patent microfilaraemia. Mastomys cells did not respond to adult or mf antigen,while adult-specific proliferation was detected in the case of gerbils. conclusion The A. viteae/gerbil model shows more similarity to human filarial infection regarding cellular immune response. Markedly low responsiveness of a high percentage of Mastomys and wide variations in the cellular response to nonspecific mitogen limit the usefulness of Mastomyscoucha in immunological studies, especially cellular immunity.

Filarial nematodes are a cause of chronic debilitating diseases in the tropics. A hallmark of filariasis is the marked down-regulation and polarization of host immune responses, yet molecular constituents of parasites causing this state have remained undefined. We describe a 17-kDa antigen (Av17) of the rodent filarial parasite Acanthocheilonema viteae, which shows amino acid homologies to cystatin C, a major cysteine protease inhibitor belonging to family 2 of the cystatin superfamily. Av17 is released by filariae in vitro. Exported molecules of A. viteae worms are shown to markedly suppress mitogen-induced T cell proliferation of mice and jirds. Av17 accounts for 45.5% of this suppressive activity in the murine system. Recombinant Av17 (rAv17), expressed in Escherichia coli, exhibits biological activity as a cysteine protease inhibitor and was used to examine the immunomodulatory effects, rAv17 induces down-regulation of murine T cell responses to mitogens, to T cell receptor cross-linking by anti-CD3 antibodies and to specific antigens, and at the same time up-regulation of interleukin-10. Hence, this filarial cystatin is a likely effector molecule of immunomodulation and a potential target for antifilarial intervention.

Three species of rodents were immunized with 50 irradiated (35 krad) stage-3 larvae (L3) of the filaria Acanthocheilonema viteae and challenged with an infection of normal L3. The immunization induced a significant reduction of the worm burden developing from the challenge infection in all host species, the jird (Meriones unguiculatus), the multimammate rat (Mastomys coucha) and the golden hamster (Mesocricetus auratus). The induced resistance was highest in jirds (92.5 +/- 9.7) followed by golden hamsters (59.4 +/- 26.6) and multimammate rats (55.1 +/- 40.4). The time course of antibody response against antigens of L3, adult worms and microfilariae, as studied by ELISA, showed quantitative and qualitative differences between the species. The antibody response against L3 antigens in immunoblots was similar in all species. Only one of the golden hamsters developed an antibody response against the surface of vector derived L3, while sera of jirds and multimammate rats did not react with L3 surface.

Dirofilaria (Nochtiella) repens is a zoonotic filarial nematode parasite of dogs and cats which is transmitted by mosquitoes (Pampiglione and Rivasi 2000). Adult worms reside in the subcutaneous tissues of infected animals and release microfilariae that circulate in the blood (Tarello 2000). Accidental infection in human beings results in subcutaneous, conjunctival and pulmonary nodules, which are often confused with tumours (Pampiglione and Rivasi 2000). In the Ukraine, 57 human cases of D repens infection have been recorded (Pavlikovskaja and others 2000), and microfilaraemia has been reported in dogs (Mazurkevich and others 2000, Vasylyk 2001) as well as cats (Pozhivil and others 2002). The finding of microfilariae is diagnostic for the presence of adult nematodes (Tarello 2003), since microfilariae detected in the blood can only originate from adult worms living in the affected animals (Pampiglione and Rivasi 2000). Microfilaraemia commonly occurs in dogs, cats and wild carnivores (wolves and foxes), which are therefore considered final hosts; adult nematodes have been recovered previously from dogs and foxes (Pampiglione and Rivasi 2000). Although cats are considered to be the final host and carriers of D repens microfilariae (Dissanaike and others 1997, Pampiglione and Rivasi 2000, Schwan and others 2000, Tarello 2003), to the authors’ knowledge there are no published reports of the detection of adult nematodes in domestic felines. This short communication describes an infestation of mature worms of both sexes in a cat from the Ukraine. An apparently healthy three-year-old male European cat from Kiev, which lived in an apartment with outdoor access, was brought to the State Veterinary Clinic of Pechersk District, Kiev, for neutering in early March 2003. During the operation, two male filarial nematodes were removed from the internal part of the scrotum and a third female parasite was removed from the spermatic cord. They were placed in physiological solution and showed spontaneous movement for up to 60 minutes, and were then fixed in 70 per cent alcohol for parasitological examination. The parasites had whitish, thread-like cylindrical bodies with rounded ends (Fig 1) showing deep, longitudinal, cuticular ridges, and a terminal mouth, which was small and round to oval shaped, without lips and surrounded by four pairs of submedian cephalic papillae. Amphidesmic cords with a double ligament were located laterally. The oesophagus consisted of two poorly limited muscular and mucosal layers. One of the male nematodes had a body length of 54·5 mm and a mean body width of 350 μm. The lengths of the spiculae (Fig 1) were 470 μm and 190 μm. The other male nematode had a body length of 60·0 mm and a mean body width of 400 μm; the spiculae were 430 μm and 210 μm long. The female nematode had a body length of 167 mm, a mean body width of 490 μm and a maximum body width of 610 μm. Microfilariae were detected in the uterus. On the basis of these features, the worms were identified as adult male and female D repens. Cats may be affected by three filarial parasites: Dirofilaria immitis, D repens and Dipetalonema grassi (Tarello 2004). Differentiation is mainly based upon clinical signs and the morphology of microfilariae, because adult nematodes are hard to find in living animals (Tarello 2000, 2003, 2004). D repens microfilariae are 325 to 375 μm in length and 6 to 8 μm wide, with a cephalic space which is roundish, short and empty. Microscopically, they are easily differentiated from other microfilariae because they are larger and longer, with a tail which is not as thin as that of D immitis (Tarello 2003). To the authors’ knowledge, this is the first report of the isolation of adult D repens nematodes in a cat. Both male and female nematodes were present and the female was pregnant, confirming that cats are a possible reservoir of D repens in the Ukraine (Pozhivil and others 2002). The nematodes were recovered from the scrotum and the spermatic cord, which is a relatively common locality in human patients from Russia (Bronshtein and others 2003). However, the concurrent occurrence of male and female parasites in the scrotum has been reported only once in human beings (Fernando and others 2000). D repens has been reported in cats from Sri Lanka (Dissanaike and others 1997), Italy (Tarello 2000, 2003) and South Africa (Schwan and others 2000) – all countries in which human cases of subcutaneous dirofilariasis have been recorded (Pampiglione and Rivasi 2000). The present feline case is the second description of D repens in a cat from the Ukraine. The first was a cat concurrently affected by Haemobartonella felis and D repens microfilaraemia and had dermatitis, exhaustion, anorexia and tachycardia (Pozhivil and others 2002), apparently confirming previous observations made on cats from Italy (Tarello 2000). The cat was born in Kiev and had never travelled abroad, indicating that the infestation was acquired locally. Compared with canine cases, reports of feline subcutaneous dirofilariosis may provide a better indication of its epidemiology, thus allowing an improved assessment of the risk of possible transmission to human beings, because cats keep to their territories more than dogs (Tarello 2003). Since 1927, 57 human cases of dirofilariasis have been reported in the Ukraine (Pavlikovskaja and others 2000). Epidemiological screenings have recently been carried out in dogs from the Ukraine (Mazurkevich and others 2000, 2001) using histochemical acid phosphatase staining of microfilariae and morphological identification of adult nematodes (Velichko and others 2000). There were 15 recorded canine cases in 1999, 130 in 2000, 188 in 2001 and 354 in 2002 (Kiev Municipality and the State Veterinary School, unpublished observations). Veterinarians are responsible for providing accurate information about the zoonotic transmission of parasite infections from pets; thus, feline subcutaneous dirofilariasis cases should be reported where possible, in order to assess the prevalence and pathogenicity of D repens in this animal reservoir. Veterinary Record (2004) 155, 638-639

The complement of fresh normal rat serum was activated by filarial eggs and microfilariae (mf). C3 was deposited on the surface of Litomosoides carinii, Brugia pahangi, Brugia malayi and Dipetalonema viteae as seen by immunofluorescence. Intra-uterine and in vitro-derived mf did not bind C3. In contrast, C3 bound to the blood-derived mf of B. pahangi and B. malayi as well as exsheathed mf of L. carinii and B. malayi. Significant consumption of complement was observed with eggs of all filarial species, as well as sheathed mf of B. pahangi, B. malayi and exsheathed mf of L. carinii and B. malayi. These experiments indicated that complement was activated by filarial parasites via the alternative pathway. The bound complement promoted neutrophil-mediated adherence and cytotoxicity.

Groups of jirds (Meriones unguiculatus), multimammate rats (Mastomys natalensis) and golden hamsters (Mesocricetus auratus) were infected with third stage larvae (L3) of Dipetaloneam viteae and the course of infection was followed until 20 weeks post infection. Worm growth was best and microfilaraemia was high and long lasting in jirds and in multimammate rats, whereas golden hamsters were poor hosts as measured by these parameters. The IgG and IgM antibody responses of the species were compared by immunoblotting and ELISA using proteins of D. viteae, separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The levels of antibodies against most proteins of high molecular weight declined during infection in jirds and in multimammate rats, whereas an increase was observed in golden hamsters. In contrast, several antigens of low molecular weight induced increasing antibody levels in all species. Species specific antigen recognition was observed for a number of protein bands of L3, microfilariae and female worms. The data suggest that susceptibility to immunesuppression and the species specific pattern of antigen recognition might determine the qualities of a rodent species as host for D. viteae.