Prevalence of Pneumonyssoides caninum infection in dogs in Sweden.

A prospective study of 474 dogs, 145 cats, and 66 wild red foxes submitted for necropsy to the Departments of Pathology at the National Veterinary Institute and the Swedish University of Agricultural Sciences, Uppsala, Sweden, was conducted to examine for the presence of Pneumonyssoides caninum, the canine nasal mite. Pneumonyssoides caninum (P. caninum) was found in 95 (20%) of the dogs but in none of the cats or foxes. The median number of P. caninum mites per infected dog was 13 (range, 1 to 250). Dogs older than 3 years of age were more often infected with P. caninum than younger dogs, and large-breed dogs were more often infected than small-breed dogs. No sex predisposition was found.

Demonstration of circulating antibodies to Pneumonyssoides caninum in experimentally and naturally infected dogs.

Antibodies to the canine nasal mite, Pneumonyssoides caninum, were demonstrated by ELISA in sera from four experimentally and 77 naturally infected dogs employing a crude P. caninum antigen. In sera from the four experimentally infected dogs, antibodies to P. caninum were first detected on day 11 post-inoculation (p.i.). Optical density (OD) values remained high throughout the observation period of 14 weeks. Two major protein bands with apparent molecular weights of 83 and 74kDa were visible by western blot (WB) from day 11 p.i. On day 14 p.i., another three major protein bands at 44, 37, and 34kDa were visible. The protein pattern then remained essentially constant until the end of the experiment except for some weak bands between 250 and 30kDa which were sometimes visible. In sera obtained from a non-inoculated control dog, no P. caninum antibodies were detected, neither by the ELISA nor by the WB. With sera from 77 naturally infected dogs with a verified diagnosis of P. caninum infection, the OD values varied between 0.24 and 0.95. When sera from four of these dogs were analysed by WB, the protein pattern observed was equivalent with that seen with sera from the experimentally infected dogs on day 25 p.i. Sera from four experimental Beagles, in which no P. caninum mites were found at necropsy, were also analysed by the P. caninum ELISA, the OD values demonstrated never exceeded 0.15. In addition, 48 sera obtained from dogs infected with or allergic to other arthropods were used for studies of possible cross-reactivity. With 10 sera, elevated OD values were found by the ELISA. Eight of them showed a similar banding pattern by the WB as did the experimentally infected dogs on day 25 p.i. This was, therefore, interpreted as an effect of a concurrent P. caninum infection.

Redescription of Parafilaria bovicola Tubangui, 1934 (Nematoda: Filarioidea) from Swedish cattle.

Parafilaria bovicola was introduced into Sweden and identified for the first time in Swedish cattle in 1978. Since then the parasite has become well established and has been responsible for substantial economic losses in Swedish beef production. Although studies have been undertaken on serodiagnosis, life cycle, vector and geographical distribution within Sweden this is the first full description of P. bovicola from Swedish cattle and the first study to use scanning electron microscopy. P. bulgarica Daskalov, 1944 is regarded as a synonym of P. bovicola Tubangui, 1934. Tooth-like thickenings described on the anterior lobes of the oesophagus for the first time may assist the parasite in its migration through the host tissues.

Diseases associated with pronounced eosinophilia: a study of 105 dogs in Sweden.

Records of 105 dogs with pronounced eosinophilia (>2.2 x 10(9) eosinophils/litre) were evaluated in a retrospective study to determine diseases associated with the abnormality in dogs in Sweden. Inflammatory disease in organs with large epithelial surfaces, such as the gut, lungs or skin, was found in 36 per cent of the dogs. A further one-quarter of the 105 cases were placed in the 'miscellaneous' category, which comprised various diseases found at low frequency. The most well defined diagnosis was pulmonary infiltrates with eosinophils in 12 per cent of the dogs. A further 11 per cent had parasitic disease caused by either sarcoptic mange or nasal mite. No atopic dog was found and rottweilers were over-represented in most disease groups. Pronounced eosinophilia, in many cases transient, seems to be associated with a variety of disorders in dogs. In the present study, rottweilers appeared to be more prone to a high eosinophil response than other breeds.

Clinical efficacy of milbemycin oxime in the treatment of nasal mite infection in dogs.

A multicentric clinical trial was done to evaluate the clinical efficacy of milbemycin oxime in the treatment of nasal mite (Pneumonyssoides caninum) infection in dogs. Milbemycin oxime was given to 70 dogs of different breeds, genders, and ages, with clinical signs associated with nasal mite infection. Twenty-five dogs had a verified infection, and 45 dogs had signs suggestive of nasal mite infection. Milbemycin oxime was given at the dosage of 0.5 to 1.0 mg/kg body weight orally once a week for three consecutive weeks. One month after initiation of treatment, 68 of the dogs had no more clinical signs associated with nasal mite infection.

Experimental infection of dogs with the nasal mite Pneumonyssoides caninum.

A successful experimental transmission of the canine nasal mite, Pneumonyssoides caninum, is described. Some 11 weeks after repeated systemic ivermectin treatment, four Beagles were inoculated via the right nostril with 20 P. caninum mites of different sexes and life stages, obtained at the necropsy of an infected dog. The inoculated dogs and a matching uninoculated control were observed for clinical signs for 14 weeks and then euthanised. Vague upper respiratory signs and a transient minor increase in the number of eosinophils in peripheral blood were recorded in the inoculated dogs. At necropsy 4-12 P. caninum mites were found in the nasal cavities and sinuses of the inoculated dogs, but none in the control. In three out of the four infected dogs mites were found in both the right and left nasal cavities and sinuses of the skull. Since in no case more mites than the number used for inoculation were detected it is not clear if the mites managed to reproduce in the dogs. Inflammatory lesions were seen most consistently in the olfactory mucosa, respiratory mucosa and tonsils, and growth of opportunistic bacteria was observed in the tonsils of the infected dogs. The inflammatory lesions seen in the olfactory mucosa may explain why dogs infected with P. caninum sometimes appear to suffer from impaired scenting ability.

Parafilariosis in African buffaloes (Syncerus caffer).

This is the first report on the occurrence of Parafilaria bassoni in the African buffalo (Syncerus caffer). Previously this parasite has been recorded only in springbok (Antidorcas marsupialis) in Namibia. Haemorrhagic perforations (bleeding points), the usual lesions seen in infected animals, were caused by gravid female parasites ovipositing embryonated eggs. These lesions occurred mainly on the dorsal and lateral sides of buffaloes. Complications of these lesions developed in a small number of buffaloes because of secondary bacterial infection [subcutaneous abscesses (3/178)] and as a consequence of a localized Type 1 hypersensitivity [large cutaneous ulcers (7/178)]. Red-billed oxpeckers (Buphagus erythrorynchus) appeared to play an important role in the epidemiology of this parasite as well as in the pathogenesis of the lesions. They reduced the likelihood of spread by ingesting blood containing embryonated eggs, and caused the development of large ulcers by feeding on superficial necrotic skin. From the results of an ELISA test it was determined that P. bassoni-infected buffaloes occur throughout the Kruger National Park complex, with a seroprevalence of approximately 34%.

Clinical picture and antibody response to experimental Sarcoptes scabiei var. vulpes infection in red foxes (Vulpes vulpes).

Three red foxes (Vulpes vulpes) were experimentally infected with Sarcoptes scabiei isolated from a naturally infected wild red fox. A fourth red fox served as a control. The first signs of sarcoptic mange became evident on the 31st day post infection (dpi). The signs gradually increased thereafter and between dpi 49 and 77 characteristic lesions of hyperkeratosis developed. Two of the infected foxes developed severe sarcoptic mange, and one of these animals died on dpi 121. The third fox developed a chronic hyperkeratotic lesion on its back, at the site where the mites had been applied. On dpi 127 the surviving foxes were treated systemically with ivermectin, and within 4 weeks the skin lesions had healed except on the pinnae of one animal. Antibodies to S. scabiei var. vulpes were demonstrated in the infected foxes by an ELISA with which seroconversion was seen around 4 weeks post infection (wpi). Western blot analysis of sequential sera of the infected animals demonstrated antibody activity consistently after the 2nd wpi. The fourth, non-infected, fox did not show any skin lesions throughout the experimental period nor any specific antibodies to S. scabiei var. vulpes.

Characterization and purification of Parafilaria bovicola antigens by chromatofocusing to enhance specificity in serodiagnosis.

A study was conducted to determine if the purification of Parafilaria bovicola antigens can increase the specificity of serodiagnosis of parafilariasis in enzyme-linked immunosorbent assay. Antigens released from adult worms of P. bovicola were separated by chromatofocusing on a polybuffer exchanger of the pH range 7.3-4.0 Polypeptide analysis by sodium dodecyl sulphate polyacrylamide gel electrophoresis showed the presence of four major polypeptides with MWs of 41, 36, 24 and 20 kDa. Additional biochemical characterization identified the 24- and 20-kDa polypeptides as hydrophobic glycoproteins. The chromatofocusing purification procedures were also applied for separation of a whole-worm extract. Again, the 41- and 36-kDa antigens were identified in separate peak fractions. Using ELISA, it was shown that the 41- and 35-kDa antigens were recognized by bovine antibodies specific for P. bovicola, but not by other sera collected from cattle infected by Onchocerca gutturosa, Onchocerca lienalis, Ostertagia ostertagi and Dictyocaulus viviparus. The serological evaluation strongly suggests that the 41- and 36-kDa antigens are P. bovicola specific.

Preparation and evaluation of the specificity of Parafilaria bovicola antigen for detection of specific antibodies by ELISA.

An enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies in bovine sera against Parafilaria bovicola nematodes was developed and its sensitivity was compared with the immunodiffusion (ID) method. An exoantigen of P. bovicola which was shown to contain four major polypeptides was used in these procedures. The serological reactivity of the antigen polypeptides was defined by using the enzyme-linked immunoelectrotransfer blot technique (EITB) and whole-worm extract proteins. It identified only four serologically reactive polypeptides with sera from one experimentally infected calf and a verified field case. These two positive sera reacted mainly with four major antigens which coincided in molecular weights of the polypeptides of the exoantigenic preparation, namely, 43, 39, 28 and 25 KDa. Calves experimentally infected with P. bovicola showed a positive reaction with ELISA at 4 months after inoculation, and after this period a rapid increase in serum antibody response occurred. In these cases the ID reaction was observed for the first time at 7 months after inoculation. The specificity of an ELISA method using crude exoantigen preparation of P. bovicola was tested for the diagnosis of bovine parafilariasis. No cross-reactivity was detected when the P. bovicola exoantigen preparation was tested against sera from calves experimentally infected with Onchocerca lienalis, as well as against the sera from cattle naturally infected with Dictyocaulus viviparus or from cattle chronically infected with Ostertagia ostertagi. In addition, testing of 740 field sera from cattle in areas non-endemic and endemic for P. bovicola indicated a specificity of the antigen preparation used. Forty sera from laboratory-confirmed field cases of P. bovicola infection were tested by ELISA and immunodiffusion. All of these sera were ELISA positive, whereas only 70% of these were positive in the ID test. Seven (2.1%) of 328 sera from 21 herds from non-endemic P. bovicola areas were ELISA positive, as opposed to none in the ID test. Of the 94 sera from six herds in areas endemic for P. bovicola infection, 51 (54%) were ELISA positive whereas only 24 (26%) were positive in the ID test. When 56 slaughtered cattle, with varying degrees of meat condemnations due to parafilariasis, were tested for P. bovicola specific antibody, 91% of the serum samples were positive by ELISA. These results suggest that the exoantigen of P. bovicola can be used in a sensitive and reliable serological detection of parafilariasis by ELISA.

The control of Parafilaria bovicola transmission in South Africa.

Ivermectin treatment of all cattle on a badly infected farm failed to interrupt the transmission of P. bovicola, even though ovipositional blood spots were drastically reduced in numbers for an entire summer season following treatment. Regular weekly to fortnightly dipping of all cattle in 50 ppm deltamethrin immediately reduced vector fly numbers to less than 1 fly per cow face. Sustained dipping for 9 months effectively reduced P. bovicola transmission from approximately 50% to less than 2%. However, cessation of fly control led to a return to predipping P. bovicola infection levels. Ovipositional blood spot counts and the ELISA technique for evaluating P. bovicola infection in a herd were compared and were both effective methods. Best results for the blood spot method, however, are obtained in spring at the peak of the bleeding season whereas the ELISA method does not have this limitation.

Parafilaria bovicola (Tubangui 1934) in cattle: epizootiology-Vector studies and experimental transmission of Parafilaria bovicola to cattle.

Parafilaria bovicola (Tubangui 1934), a filarial nematode, causes cutaneous bleedings of live cattle and bruise-like lesions in the subcutaneous and IM surfaces of affected carcasses. To determine the vector(s) of this nematode under Swedish conditions, a field survey was conducted during the pasture season, May-September 1980. A total of 9,931 insects were collected from cattle and subsequently examined for infective 3rd stage Parafilaria larvae. From the fly species collected. Musca autumnalis (De Geer), Hydrotaea irritans (Fall), and Haematobia stimulans (Meig) were those most frequently identified. The 3rd-stage larvae were only found in M autumnalis, face fly. Overall infection rate in these flies was 3.5%, with peak prevalence of 30% in June. Most of the nematode larvae were recovered from heads of female flies. In experiments in insect-free stables, 5 calves were experimentally inoculated with infective 3rd-stage P bovicola larvae. Two calves inoculated by the intraconjunctival route (larvae were instilled inside the eyelid) became infected, whereas 3 calves injected subcutaneously did not. Signs of infection were not seen in 4 control calves. The median development period of P bovicola from infective 3rd-stage larvae to the development of bleeding points was 43 weeks (301 days) in 26 cattle with spontaneous parafilariasis.