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Biomedical subjects

A J Trees

Publications and source records attributed to A J Trees.

At least 19 recordsLinked to original sources
PubMed1998

Acute phase toxoplasma abortions in sheep.

Within 13 days of the experimental infection of 15 oestrus-synchronised ewes with 2000 sporulated oocysts of Toxoplasma gondii at 80 to 90 days of gestation 11 had aborted. The infection induced pyrexia and specific antibody in all the ewes. One ewe resorbed its fetus, 11 ewes aborted and three delivered, at full term, live congenitally infected lambs whose pre-colostral serum was antibody-positive. Tissues from the aborted fetuses and placentae from the live lambs were examined for toxoplasma infection by polymerase chain reaction (PCR) amplification of the B1 gene and by mouse inoculation. The live lambs were all shown to be infected by both methods, but there was no evidence of infection in any of the tissues from the acute phase abortions, suggesting that these fatalities occurred before the placenta or the fetus had been invaded by T gondii. Such toxoplasma-induced, acute-phase abortions are likely to be impossible to diagnose from fetal tissues. These results have implications not only for the diagnosis of naturally occurring ovine abortions but also for the understanding of the pathogenesis of toxoplasma-induced abortion.

Abortion, Veterinary↗
PubMed1998

Diagnosis of toxoplasma abortion in ewes by polymerase chain reaction.

Eighteen oestrus-synchronised ewes were infected experimentally with 1500 sporulated oocysts of Toxoplasma gondii between 80 and 90 days of gestation. The infection induced pyrexia and specific antibody in all the ewes. One ewe resorbed its fetus, five ewes aborted and 12 delivered live, congenitally-infected lambs whose pre-colostral serum was antibody-positive. Tissues from the aborted fetuses and placentae from the live lambs were examined for toxoplasma infection by polymerase chain reaction (PCR) amplification of the B1 gene and by mouse inoculation. Using a simple protocol of tissue preparation without DNA extraction and a nested format, PCR was as sensitive as mouse inoculation. Placental cotyledon gave a higher sensitivity of detection than brain, lung or liver, and 16 of 19 placentae were positive by PCR compared with 13 of 18 by mouse inoculation. In mock-infected tissues, as few as 10 tachyzoites could be detected. The PCR could be applied to tissues unfit for mouse inoculation.

Abortion, Veterinary↗
PubMed1998

Naturally occurring vertical transmission of Neospora caninum in dogs.

Vertical transmission of Neospora caninum was studied in naturally infected, privately owned dogs, using antibody detection by IFAT to identify infected individuals. Retrospective studies were undertaken in litters from six bitches of the Hamiltonstövare breed, and on litters from seven bitches of other breeds--in both cases following diagnosis of clinical disease in puppies--and prospective studies were carried out on 17 seropositive bitches of other breeds. Puppies were classified as infected if either pre-colostral sera, or serum taken at > or = 5 weeks, had a titre of > or = 1:50 in the IFAT. The frequency of putative congenital transmission was variable; three seropositive dams produced successive litters, each containing seropositive puppies; four other seropositive bitches, which each whelped twice, produced six litters in which all pups were seronegative. Bitches born to seropositive dams themselves produced litters containing seropositive pups. In the retrospective studies, 32/61 (52%) of pups tested born to 13 seropositive dams were themselves seropositive and 22/88 (25%) of all pups born developed clinical signs compatible with a diagnosis of neosporosis. However, in the prospective study, only 4/118 (3%) pups tested from 17 seropositive dams were seropositive and 4/122 (3%) of all pups born developed signs consistent with neosporosis. This difference reflected levels of IFAT titre in the two groups of bitches and overall the proportion of pups seropositive was strongly and positively correlated (r = 0.980, P < 0.05) with bitch IFAT titre. Overall, 80% of pups born to seropositive dams were not infected as determined serologically. This study shows that the frequency of vertical transmission of naturally acquired Neospora infection in dogs is variable, but much too low to sustain infection alone. Post-natal infection must occur to maintain infection at seroprevalence rates reported in dog populations.

Animals↗
PubMed1998

Vertical transmission of Toxoplasma gondii from chronically infected house (Mus musculus) and field (Apodemus sylvaticus) mice determined by polymerase chain reaction.

Captive-bred Mus musculus (house mice) and Apodemus sylvaticus (field mice) were each infected with 50 oocysts of Toxoplasma gondii M1 strain per os and infection in them and their offspring was assessed by polymerase chain reaction (PCR) amplification of the T. gondii B1 gene in brain tissue and by serology, using the modified agglutination test (MAT). The chronically infected female A. sylvaticus (n = 10) and M. musculus (n = 23) were mated at least 6 weeks after infection (and subsequently to produce up to 6 litters) and their pups examined 3 weeks after weaning at 6 weeks of age. By PCR, in offspring of A. sylvaticus and M. musculus respectively, vertical transmission was demonstrated in 82.7% (n = 83) and 85.0% (n = 207) of all pups (N.S., P > 0.05), 95% (n = 21) and 100% (n = 30) of all litters (N.S., P > 0.05), with a mean (+/- S.E.) proportion of each litter infected of 0.87 (0.06) and 0.86 (0.04) (N.S., P > 0.05). There was no change in any of these variables between first and subsequent litters. By serology, whilst MAT suggested 100% vertical transmission in A. sylvaticus, it under-estimated rates of infection in offspring of M. musculus. A limited series of bioassays from M. musculus tissues confirmed the good correlation of PCR and the poor correlation of MAT with mouse inoculation. These results indicate that vertical transmission in A. sylvaticus and M. musculus is extremely efficient and probably endures for the life of the breeding female. This mechanism favours parasite transmission and dispersion by providing a potential reservoir of infection in hosts predated by the cat.

Agglutination Tests↗
PubMed1998

Tapeworm infection is a significant risk factor for spasmodic colic and ileal impaction colic in the horse.

The association between the equine intestinal tapeworm Anoplocephala perfoliata and specific types of intestinal disease was investigated by matched case-control study using coprological and serological diagnosis. We have previously shown that the host IgG(T) response to 12/13 kDa antigens of A. perfoliata correlates well with infection intensity, therefore this antibody response was used to investigate the risk of colic at different levels of parasite infection intensity. One hundred and three spasmodic colic cases with an equal number of controls matched for age, breed and gender, and 20 ileal impaction cases each with 2 similarly matched controls were obtained. Cases of spasmodic colic were much more likely (odds ratio = 8.0) to be associated with A. perfoliata infection detected coprologically than controls. Serological diagnosis revealed an increasing risk of spasmodic colic with increasing infection intensity. Calculation of an aetiological fraction suggests that 22% of spasmodic colic cases in this study were tapeworm associated. No significant association was found between colic and strongyle egg count. Conditional logistic regression analysis demonstrated that the relationship between colic and A. perfoliata infection intensity was not confounded by strongyle egg count and there was a linear relationship between infection intensity and the log-odds of spasmodic colic. For cases of ileal impaction, a strong association was found between colic and A. perfoliata as diagnosed by coprological means (odds ratio of 34.0). Serological diagnosis also revealed a strong association that increased with higher levels of infection intensity (odds ratio = 26.0). The aetiological fraction for the ileal impaction data suggests that 81% of the ileal impaction cases in this study were tapeworm associated. This study concludes that A. perfoliata is a significant risk factor for spasmodic colic and ileal impaction colic in the horse; and that the risk of spasmodic colic increases with infection intensity.

Animals↗
PubMed1997

Comparison of histology with maternal and fetal serology for the diagnosis of abortion due to bovine neosporosis.

An indirect fluorescent antibody test was applied to sera from normally calving and aborting cows and to samples of pleural fluid from their aborted calves, and the antibody titres were compared with histology and immunocytochemistry for the diagnosis of Neospora-associated abortion. Two groups of aborting cows and a third group of cows which had calved normally were used; group A consisted of 36 cows which aborted calves showing characteristic non-suppurative inflammatory lesions in which Neospora was demonstrated by immunocytochemistry, group B consisted of 100 cows which aborted calves without histological evidence of neosporosis, and group C consisted of 128 normally calved cows which were sampled within one month of calving. Serology on the maternal sera and fetal fluids was highly specific and sensitive for Neospora infection although 5 per cent of the cows which aborted Neospora-negative calves and 4.7 per cent of the normally calved cows were also seropositive. Anti-Neospora antibodies were also detected in 7 per cent of the samples of fetal fluid from Neospora-negative abortions.

Abortion, Veterinary↗
PubMed1997

Novel ELISA for detection of Neospora-specific antibodies in cattle.

An enzyme-linked immunosorbent assay (ELISA) to detect antibodies to Neospora species in cattle was developed. Whole formalin-fixed Neospora caninum (NC-Liverpool) tachyzoites were used as antigen and a monoclonal antibody to bovine immunoglobulin light chain and an anti-mouse horseradish peroxidase conjugate were used to reveal bound antibody. A panel of 46 sera, negative by the immunofluorescent antibody test (IFAT), were used in the ELISA at a serum dilution of 1:500 to calculate the negative cut-off value of OD405 = 0.77. There was a 95 per cent agreement between the results of the ELISA and the IFAT with 104 serum samples. The specificity and sensitivity of the ELISA were 96 per cent and 95 per cent, respectively, when compared with the IFAT. No significant cross-reaction was observed with the sera from cattle infected experimentally with Toxoplasma gondii, Cryptosporidium parvum, Babesia divergens, Sarcocystis cruzi, Eimeria alabamensis or E bovis. A significantly modified version of the test is now commercially available.

Animals↗
PubMed1997

Results of a survey to determine whether Neospora is a significant cause of ovine abortion in England and Wales.

Between January and April 1995, the brains and hearts of 281 aborted lambs derived from 209 submissions to veterinary investigation centres in England and Wales were examined histologically. One-hundred-and-seventy-nine samples of fetal pleural fluid from these lambs and 141 from lambs not examined histologically were examined for antibodies to Neospora by an indirect fluorescent antibody test. Non-suppurative myocarditis and encephalitis were present in nine lambs. Immunocytochemistry using antisera against Neospora caninum and Sarcocystis species resulted in no labelling but anti-sera to Toxoplasma gondii revealed labelled organisms in four lambs. No significant antibody titres against Neospora were detected in any of the samples of fetal pleural fluid. These results suggest that Neospora infection is not associated with significant numbers of abortions in sheep in England and Wales.

Abortion, Veterinary↗
PubMed1997

Experimental infection of non-pregnant and pregnant sheep with Neospora caninum.

In an initial experiment, 21 sheep in groups of five or six were inoculated subcutaneously (sc) with 10(8), 10(6) or 10(4) Neospora caninum tachyzoites (Liverpool isolate), or with control inoculum, and monitored for clinical signs and for "seroconversion". Animals given the two higher doses showed febrile responses and all three groups inoculated with the parasite showed seroconversion. In a second experiment, 12 pregnant sheep were each inoculated sc at 90 days' gestation with 10(6) tachyzoites, and at 25, 40 and 53 days post-inoculation (dpi) groups of four were killed for examination of the fetuses and placentas. Appropriate control ewes were included in the study. All fetuses were alive immediately before their dams were killed, except for one, which was found to be mummified at 40 dpi. Histopathological lesions were found consistently in both fetal central nervous system (CNS) and placental tissues. In the latter, focal necrosis, which was mild at 25 dpi, was much more severe at 40 dpi and much less severe at 53 dpi. Lesions in the fetal CNS consisted of focal microgliosis (with or without central necrosis), lymphoid cuffing and non-suppurative meningitis. Lesions were also found in fetal liver, heart and lung. Neospora antigen was demonstrated in fetal brain and placental tissues and, at 25 dpi, in single samples of fetal liver and heart. The prescapular lymph nodes did not differ in size from those of control fetuses but were more mature in that they contained a significantly greater number of secondary follicles. Both IgM and IgG antibodies to N. caninum were detected in the serum of fetuses from infected ewes. Thus, N. caninum readily infected pregnant ewes and caused lesions in fetal tissues and placentas which resembled those of ovine toxoplasmosis. In addition, the changes were similar to those of bovine neosporosis; the infected pregnant ewe therefore offers a good model for the bovine disease.

Animals↗
PubMed1997

Immunoepidemiology of the equine tapeworm Anoplocephala perfoliata: age-intensity profile and age-dependency of antibody subtype responses.

The equine intestinal cestode Anoplocephala perfoliata has been the subject of recent epidemiological and immunological studies because of its suspected association with intestinal disease in the horse. We have previously shown that the IgG(T) subtype antibody response to the 12/13 kDa component of the parasite excretory/secretory (E/S) antigen is positively correlated with parasite intensity. In this study, we utilize that correlation to examine the changes in natural infection intensity with age. Infection intensity based on IgG(T) responses showed a triphasic age-dependency pattern with peak mean worm burden in the 6 months-2 years age group, falling to a lower plateau level from 3 to 15 years, and rising again in older age groups. Anti-E/S total IgG was found to have a convex age-dependency curve, with maximal response in the 6 months-2 years old age group. IgG(a) showed a triphasic response similar to the age-intensity profile of IgG(T); IgG(c) showed steadily increasing levels of antibody with age. The IgG(b) age-dependency profile was intermediate between IgG(a) and IgG(c). Age-specific correlation coefficients between anti-12/13 kDa IgG(T) (as a measure of infection intensity) and IgG(a) and IgG(b) revealed statistically significant values for many age groups. The relative importance of exposure to infection and the development of acquired immunity as determinants of the observed age-intensity pattern is considered.

Age Factors↗
PubMed1997

The entry of ivermectin and suramin into Onchocerca ochengi nodules.

No currently available drug, which is safe for mass treatment, effectively kills adults of Onchocerca volvulus, the causal agent of onchocerciasis in humans, or of O. ochengi, a cattle parasite used as a model of O. volvulus. Since adults of both of these filarial nematodes are found in well developed nodules, the lack of efficacy of these drugs may be a result of their poor penetration into the nodules. To check if this was the problem, the distributions of the microfilaricide, ivermectin, and the partial macrofilaricide, suramin, in plasma, skin, nodule capsules and nodule contents were determined in cattle naturally infected with O. ochengi in Cameroon. The cattle were treated with either a single, subcutaneous injection of 500 micrograms ivermectin/kg, or with intravenous injections of [14C]-labelled suramin, each of 10 mg/kg, given one a day for 6 days. Concentrations of ivermectin and suramin in various tissues were then assayed by high-pressure liquid chromatography and scintillation counting, respectively. On day 7 post-treatment (pt), suramin concentrations were consistently highest in the nodule, contents and capsule wall (11.0 and 8.9 nCi/g, respectively) and significantly less in skin and plasma (1.2 and 1.4 nCi/g, respectively; P < 0.05). The distribution of ivermectin on day 7 pt was similar, with the highest concentrations in the capsule wall, nodule contents and plasma (58.4 ng/g, 43 ng/g and 48.6 ng/ml, respectively; P > 0.05) and the concentration in the skin (6.4 ng/g) significantly lower than those in the capsule or plasma (P < 0.05). High intra-nodular concentrations of both drugs were maintained for 5-7 days at least and those of ivermectin would be expected to kill nematodes other than filariae. It is apparent that failure of ivermectin and suramin to kill adult Onchocerca spp. is not because the drugs penetrate nodules inadequately.

Animals↗
PubMed1997

Seroprevalence of antibodies to Neospora caninum in Belgian dogs.

Sera from 300 dogs from Ghent and Antwerp were tested for antibodies to Neospora caninum using an indirect fluorescent antibody test. Overall, 11 per cent (9.5 to 13 per cent; confidence interval of 95 per cent) of dogs were seropositive, at titres of 1:50 to 1:800. No sex or breed differences were detected, but there was an increase in seropositivity with age.

Aging↗
PubMed1997

Prevalence of antibodies to Neospora caninum in different canid populations.

A total of 1,554 dogs from 5 countries on 3 continents were tested for antibodies to Neospora caninum using an indirect fluorescent antibody test. In Australia, overall, 42/451 (9%, 95% confidence interval [CI] 6-12%) dogs were seropositive (Melbourne 11/207 [5%, 95% CI 2-9%]; Sydney 18/150 [12%, 95% CI 7-18%]; Perth 13/94 [14%, 95% CI 8-22%]). Antibodies to N. caninum were also detected in dogs in South America (Uruguay [20%, 95% CI 16-24%, n = 414]) and sub-Saharan Africa (Tanzania [22%, 95% CI 12-36%, n = 49]). In contrast, only 1 of 500 dogs tested from the Falkland Islands and none of 140 dogs from Kenya was seropositive. Of wild canids, 1/54 (2%, 95% CI 0-10%) British foxes and 15/169 (9%, 95% CI 5-14%) Australian dingoes had antibodies to N. caninum.

Africa, Eastern↗
PubMed1996

Clinical aspects of 27 cases of neosporosis in dogs.

Twenty-seven cases of neosporosis in European dogs are described. The disease was confirmed by immunohistochemistry, electron microscopy, or a favourable response to treatment in the dogs with appropriate clinical signs, and by the presence of antibodies to Neospora caninum but not to Toxoplasma gondii. The affected dogs were two days to seven years old, and of 13 different breeds. Both sexes were affected and in most cases littermates remained normal. Twenty-one cases had an initial hindlimb paresis or ataxia, in which muscle atrophy was the most consistent clinical sign. Rigid hyperextension developed in approximately half of the cases. Anorexia and pyrexia were rare. Other clinical signs included forelimb ataxia, head tremors with tetraparesis and sudden collapse due to myocarditis. Titres of > or = 1:800 in the N caninum indirect fluorescent antibody test were detected in the 20 cases from which serum samples were taken. Such high titres are rare in healthy dogs and strongly suggest a diagnosis of neosporosis. Sixteen of the dogs received appropriate antiprotozoal treatment with clindamycin, potentiated sulphonamides and/or pyrimethamine; 10 made a full or functional recovery. Recovery was less likely in peracute cases with severe clinical signs, and when the treatment was delayed.

Animals↗