Experimental infection of European red foxes (Vulpes vulpes) with canine herpesvirus.

We report on the pathogenicity of canine herpesvirus (CHV) for European red foxes. In the first experiment, we inoculated 10 adult foxes intravenously with a canine isolate of CHV. All foxes became infected and shed CHV in saliva and genital secretions for up to 14 days post-inoculation (p.i.) as evaluated by PCR and/or by virus isolation. All foxes developed clinical signs such as fever, lethargy and evidence of respiratory tract disease. Two foxes died on day 6 p.i., one on day 7 p.i., and one fox was euthanased on day 6 p.i. Tissues taken from the four dead foxes were positive for CHV by PCR. The remaining six foxes recovered after approximately 14 days p.i. Virus particles with morphology typical of herpesviruses were found by electron microscopy in the liver of an infected animal. All surviving foxes developed serum anti-CHV antibodies. In a second experiment, six foxes were dosed perorally with CHV and paired with six untreated controls. Neither the perorally dosed nor the in-contact control foxes developed clinical signs of disease. Infectious CHV was not isolated from any of the dosed or the in-contact foxes but all perorally-infected foxes and one of the in-contact foxes tested PCR-positive for CHV on several occasions p.i. All perorally-infected foxes, but none of the in-contact foxes, seroconverted. In summary, intravenous CHV inoculation caused a clinical disease in adult foxes much more severe than observed in experimentally-infected adult dogs. No clinical disease or virus spread was observed after peroral dosing although viral infection occurred as evidenced by seroconversion.

Aplasia of the gallbladder in a dog.

A young, female Maltese dog was presented with intermittent vomiting of bile. Biochemical evidence of persistent mild hepatopathy had been present for 11 months. Exploratory celiotomy was performed. Absence of the gallbladder with malformation of the quadrate lobe of the liver was identified. There was histological evidence of bile duct proliferation and portal fibrosis.

In vitro leucocyte proliferative responses and lymphocyte sub-types in guinea pigs with genetically determined high- and low-level responsiveness to Trichostrongylus colubriformis.

In vitro leucocyte proliferative responses to parasite antigens and to mitogens as well as lymphocyte sub-types were compared in guinea pigs with genetically determined differences in their ability to express protective immunity against Trichostronylus colubriformis infection. Proliferative responses to parasite antigens were greatest in high-responder (HR) animals, but cells from low-responder (LR) animals were generally more responsive to mitogens. However, HR circulating leucocytes were more responsive to the T-cell-dependent B-cell mitogen pokeweed mitogen (PWM), and the response of HR, but not LR, cells increased during primary infection with T. colubriformis. Flow cytometry revealed significantly greater numbers of circulating B-cells in HR animals and, as observed for responsiveness to PWM, the number of circulating B-cells increased in HR, but not LR, animals during primary infection with this parasite. These findings suggest a larger and more labile population of B-cells in HR guinea pigs.

Antibody production in guinea pigs with genetically determined high and low responsiveness to Trichostrongylus colubriformis.

Antibody levels were compared in guinea pigs with genetically determined differences in their ability to generate protective immunity against the small-intestine nematode parasite Trichostrongylus colubriformis. Animals with the most effective immune response (high responders) developed significantly higher anti-T. colubriformis IgG1 antibody titres than low-responder animals. However, there were no significant differences between their IgG1 antibody responses to a systemically administered protein antigen (ovalbumin). High-titre anti-T. colubriformis serum from high-responder animals did not transfer significant passive protective immunity to low-responder recipients. It is suggested that anti-T. colubriformis IgG1 antibodies mediate the release of mast-cell and basophil products at the site of infection and thus contribute to the more effective immunity expressed by high-responder animals.

Quantitative and qualitative changes in intestinal goblet cells during primary infection of Trichostrongylus colubriformis high and low responder guinea pigs.

Small intestine goblet cell numbers and the composition of their mucus were compared in guinea pigs with genetically determined differences in responsiveness to Trichostrongylus colubriformis infection. Prior to infection, no differences between high responder and low responder animals were detected. However, following primary infection with T. colubriformis, pronounced goblet cell hyperplasia developed and the proportion of sulphomucin in these cells increased. Both changes developed significantly earlier in high responder animals.

Differential expression of interleukin-5 mRNA+ cells and eosinophils in Nippostrongylus brasiliensis infection in resistant and susceptible strains of mice.

Interleukin (IL)-5 is produced by both T cells and eosinophils and has been implicated in lymphocyte and eosinophil differentiation and maturation. The extent to which differences in IL-5 expression contribute to genetic variability in parasite immunity was investigated by comparing eosinophilia, IgE production, mastocytosis and IL-5 mRNA+ cells following Nippostrongylus brasiliensis infection of resistant (BALB/c) and susceptible (C57BL/6) mice. In uninfected mice, IL-5 mRNA+ cells detected by in situ hybridization were distributed throughout the lamina propria and crypt regions of the small intestine in both strains, but were 1.5-fold higher in BALB/c than in C57BL/6 mice. Following N. brasiliensis infection, the numbers of IL-5 mRNA+ cells in BALB/c mice continued to increase until day 11 post-infection at which time they were more than 4-fold more numerous than in uninfected control mice of the same strain. In C57BL/6 mice, IL-5 mRNA+ cells reached peak numbers on day 7 post-infection, only 1.5-fold higher than uninfected controls, but the numbers began to decline thereafter. At all time points after day 5, the numbers of IL-5 mRNA+ cells in the gut of C57BL/6 mice were significantly lower than BALB/c mice. The differences in numbers of IL-5 mRNA+ cells induced by infection in each strain of mice correlated with changes in blood and intestinal eosinophilia, mastocytosis and IgE production and was reflected in differences in worm expulsion and egg counts. Although numbers of intestinal IgA-containing cells increased in both strains after infection, there was no difference between strains except at day 11 when there were significantly higher numbers in BALB/c mice than in C57BL/6 mice. These results suggest that IL-5 is an important regulatory factor determining host immunity to parasite infection and that differential regulation of IL-5 expression explains in part the observed strain differences with respect to parasite resistance.

Glomerulopathy in dogs with congenital portosystemic shunts.

Kidney specimens from 12 dogs with congenital portosystemic shunts were examined histologically. Glomerulopathy of variable severity was present in the kidney sections of all 12. Marked irregular thickening of the glomerular capillary wall was the most prominent pathological change, the renal interstitium being largely unaffected. The severity of lesions was not correlated with the age of dogs at the time of necropsy. An immunoperoxidase technique failed to demonstrate significant IgA or IgG deposition in affected glomeruli. Proteinuria was generally mild or absent despite significant glomerular lesions, except in dogs with concurrent urinary tract infection.

Effect of Freund's adjuvants on guinea pigs infected with, or vaccinated against, Trichostrongylus colubriformis.

Soluble antigens that protected guinea pigs against experimental challenge with Trichostrongylus colubriformis were found to be less effective if injected as emulsions in Freund's adjuvants. This occurred despite the production of higher antibody titres in guinea pigs given emulsified antigen. Investigations of this phenomenon showed that an intraperitoneal injection of Freund's complete adjuvant (FCA) delayed rejection of primary infections and partially abrogated resistance to challenge infection. Administration of FCA/antigen emulsion to infected guinea pigs resulted in a prolonged blood eosinophilia which paralleled the increased longevity of the parasitosis. These findings suggest the need for caution in the selection of adjuvants for vaccination against gastrointestinal nematodes.

Expulsion of Trichostrongylus colubriformis by high and low responder guinea-pigs.

Guinea-pigs with genetically determined susceptibility to infection with Trichostrongylus colubriformis (or low responders) rejected both primary and secondary infections with this parasite more slowly than resistant animals (high responders). Low responders were not protected with a vaccination procedure which was highly effective in outbred animals. The relatively poor protective immune responses that develop in low responder guinea-pigs are evocative of the responses of the natural host to infection with this parasite and suggest that low responder guinea-pigs have potential for the study of T. colubriformis protective antigens and for the development of adjuvants to enhance antiparasitic effector responses in vaccinated hosts.

Basophil leucocytes in responses to parasitic infection and some other stimuli in sheep.

Basophil leucocytes are a significant component of the infiltrating cells in a variety of tissue reactions in guinea pigs. However, little is known about the participation of basophils in similar reactions in most other animal species. The circulating blood, skin and small intestinal mucosa of sheep were examined after they had received stimuli known to elicit basophil-rich responses in guinea pigs but relatively few basophils were found.

Differences in eosinophil migration into the lungs following inhaled antigen challenge of parasite-naive guinea pigs with genetically determined differences in responsiveness to a gastrointestinal nematode parasite.

Parasite-naive guinea pigs with genetically determined differences in responsiveness to infection with the gastrointestinal nematode parasite Trichostrongylus colubriformis were sensitised to ovalbumin and later challenged by exposure to an ovalbumin aerosol. The resultant cellular migration into the lungs was assessed by histological examination of the lungs and enumeration of cells in bronchoalveolar lavage fluid 24 h, 72 h and 7 days later. Compared with parasite-low-responder guinea pigs, there were approximately 10 times more eosinophils in lavage fluid from parasite-high-responder animals but similar numbers of neutrophils.

Relationship between eosinophilia and responsiveness to infection with Trichostrongylus colubriformis in sheep.

Lambs with genetically determined increased immunological responsiveness to Trichostrongylus colubriformis (high responders) had more eosinophils in cutaneous reactions to the mitogen phytohaemagglutinin (PHA) both before and during infection compared with those bred for susceptibility (low responders). In contrast, eosinophil numbers in both blood and cutaneous reactions elicited by third-stage T. colubriformis larval antigen were similar in high and low responders before infection. Following vaccination and challenge, high responders had elevated eosinophil numbers in blood and antigen-stimulated skin. In unselected sheep, although eosinophil numbers in cutaneous reactions to PHA were related to responsiveness to a challenge infection with T. colubriformis, there was a closer relationship between blood eosinophil numbers and responsiveness. Infection with T. colubriformis increased eosinophil numbers in cutaneous reactions to PHA and appeared to augment the difference between eosinophil counts in high and low responder sheep. Measurement of the ability to produce eosinophil activating factors, or for eosinophils to respond to such factors might therefore be useful in identifying individual sheep with increased responsiveness to T. colubriformis infection.

Calcifying tendinopathy of the biceps brachii in a dog.

Calcifying tendinopathy of the biceps brachii was associated with lameness in a 1.5-year-old Rottweiler. Lameness was relieved by excision of the calcified mass and suture repair of the partially ruptured tendon. Calcifying tendinopathy is not well described in dogs, but it is a recognized clinical syndrome in human beings. The etiopathogenesis of the condition in human beings and dogs is poorly understood. Wider recognition of calcifying tendinopathy in dogs should lead to a better understanding of the disease and development of appropriate clinical treatments.

The effect of specific immunization or infection with Trichostrongylus colubriformis on production of eosinophil differentiation factors in guinea pigs.

The cultivation of bone marrow was used to quantitate the levels of eosinophil differentiation factors (EDF) produced in conditioned medium (CM) by incubation of mesenteric lymph node cells (MLNC) with mitogens or specific antigens from the intestinal nematode parasite, Trichostrongylus colubriformis. In liquid cultures with 20 units ml-1 recombinant murine interleukin-5 (IL-5), bone marrow cells (BMC) from either normal or infected donors contained less than 5% eosinophils and differentiated to greater than 50% eosinophils over 2-3 weeks. Conditioned medium from 3-4 week infected donors produced between 20 and 50% eosinophils when donor MLNC were stimulated with the specific antigen preparation SP3, but macrophages predominated when using CM from MLNC incubated with Concanavalin A (ConA). CM from MLNC of challenged donors incubated with SP3 produced 30-70% eosinophils in BMC assays, with highest levels induced by CM from high responder (HR) donors. Marrow from parasitized or normal donors gave rise to comparable proportions of eosinophils. CM was also produced from LNC of donors given protein or parasite antigens in adjuvant where between 28 and 35% eosinophils were produced in culture. There were no differences between activities attributable to the antigen, but Freund's complete adjuvant induced earlier differentiation of BMC than alum-induced CM. The results confirm that high levels of EDF activity are specifically induced by parasitic infection, and can also be produced by intraperitoneal and subcutaneous inoculation of adjuvanted antigens. Consistent with the greater eosinophilia exhibited by HR guinea pigs to infection with T.colubriformis L3, their MLNC also produced the highest levels of EDF activity.