Recent advances in understanding the epidemiology of Neospora caninum in cattle

INTRODUCTION: Neospora caninum is the most frequently diagnosed cause of cattle abortion in New Zealand and is an important pathogen worldwide. The parasite has been found in aborted bovine foetuses and in puppies with neurological disease. Recent developments have provided new insights into the epidemiology of the disease that are reviewed in this article. TRANSMISSION: Transplacental infection is of major importance in the spread of N. caninum overseas. Most congenital infections result in the birth of apparently healthy calves. Seroepidemiological studies indicate introduced point-source infections are also likely, as do investigations of abortion outbreaks in cattle herds attributed to N. caninum. Horizontal transmission is an important determinant of the stability of infection prevalence in a herd. Two potential sources of horizontal transmission that have recently been reported are: via a canine definitive host and; cow-to-calf transmission through pooled colostrum or milk. Transmission parameters for the organism have been estimated using mathematical modeling, to explore the epidemiology and options for control of N. caninum infection in dairy cattle in the absence of precise epidemiological data. LIFE-CYCLE: Seroepidemiologic studies, combined with the knowledge that dogs can be a definitive host, provide evidence supporting a dog-cattle life-cycle. The importance of dogs in the epidemiology of bovine neosporosis is not yet clear. It is likely that N. caninum oocysts in dog faeces could serve as a source of infection for cattle and recent studies have shown that the canine and bovine isolatesflare the same organism. Infection of cattle orally exposed to oocysts has been demonstrated experimentally but not in nature. It is not known if other wild carnivores may serve as definitive hosts of N. caninum. CONCLUSION: Despite active research for over a decade, very little is known about the mechanisms of transmission of N. caninum. Vertical transmission is well documented but horizontal spread and the pathogenesis of abortion from this disease need further investigation. It is evident that, even with a very high probability of vertical transmission, some form of horizontal transmission is required for the disease to persist in a herd.     

The Use of Antigen-capture Enzyme-linked Immunosorbent Assay (ELISA) for the Diagnosis of Rinderpest and Peste des Petits Ruminants in Ethiopia

Rinderpest had been reported in most parts of Ethiopia when the Pan African Rinderpest Campaign (PARC) was launched. As a result of intensive disease investigation and strategic vaccination, most parts of the country are now considered provisionally free, and widespread vaccination has been replaced by clinical and serological surveillance. Details of any episodes of disease are recorded and followed up after laboratory confirmation of suspected cass using antigen-capture ELISA. This paper is based on observations on the performance of the antigen detection ELISA compared to the agar gel immunodiffusion (AGID) test, which also differentiates rinderpest from peste des petits ruminants (PPR). The stability of the specific viral antigen was monitored for 4 days, and rinderpest and PPR antigens were still detected, depending on the type of specimen. Antigen capture ELISA is more rapid, sensitive and virus specific than the AGID. Even if the cold chain of the specimen is compromised for a day or two during sample collection and submission, the specimen may still be suitable for testing by ELISA.     

Influence of ileo-caecal cannulation and oxytetracycline on ileo-caecal and rectal coliform populations in pigs

The effect of surgery (insertion of an ileo-caecal cannula) and a subsequent parenteral treatment with oxytetracycline on the ileo-caecal and rectal coliform populations in 7 Swedish Yorkshire castrates were studied. Samples were collected during surgery as well as 3, 7, 14 and 20 days post surgery. The diversity of the enteric coliform flora was initially high both in the ileo-caecal ostium and in rectum. No alteration in the diversity of the enteric coliform flora was observed following surgery and treatment with oxytetracycline. As the insertion of ileo-caecal cannulas did not affect the intestinal coliform flora this study gives support to the use of this technique to mirror processes in the small intestine of pigs. Further, the diversity of the enteric coliform flora was unaffected by the parenteral treatment with oxytetracycline.     

Calcification of the intervertebral discs and curvature of the radius and ulna: a radiographic survey of Finnish miniature dachshunds

The vertebral column of 124 randomly selected miniature dachshunds, representing 4.5% of the population registered by the Finnish Kennel Club during the years 1988 to 1996, were radiographed. The front legs were also radiographed in order to evaluate the curvature of the radius and ulna. Calcified discs were found in 75.9% of the longhaired miniature dachshunds and in 86.7% of the wirehaired ones. The occurrence of signs associated with IDD was 16.5% in longhaired and 15.6% in wirehaired miniature dachshunds. The occurrence of signs of IDD in dogs with calcified discs was 20.0% and 17.9% in longhaired and wirehaired miniature dachshunds, respectively. In dogs without calcifications only one dog showed signs of IDD. The curvature of the radius and the ulna did not differ between the dogs with signs of IDD and the healthy ones, or between the dogs with and without intervertebral calcifications. Our results indicate that radiographic eradication based on the presence of intervertebral calcifications is not suitable for breeding purposes for the Finnish miniature dachshund population because the percentage of dogs without calcifications is small.     

An Outbreak of Respiratory Disease Complex in Sheep in Central Ethiopia

An investigation was carried out into an outbreak of respiratory disease complex (RDC) in 3641 Menz and Awassi×Menz cross sheep in Central Ethiopia between 1998 and 1999 by clinical, serological, microbiological, post-mortem and histopathological examinations. The monthly incidence of RDC varied from 2.8% to 4.0% and the prevalence was as high as 17%. The case fatality rate was 18%, despite culling of sick sheep. Over 76% of the morbidity occurred in adults, followed by 19% among weaners. Similarly, 62% of the mortality was in adults. However, 27% of the mortality occurred in lambs despite the low morbidity in the group. Significant breed and age differences were seen in the morbidity and mortality rates (p<0.05). Clinical signs, gross and microscopic lesions and serological and bacteriological examinations showed an interplay of several causes of the RDC, including pestes des petits ruminants (PPR) (72.3%, serologically confirmed), lung worms, maedi-visna, bacterial bronchopneumonia (staphylococcal and streptococcal), enzootic pneumonia and some fungal infections. Cold temperatures, which may be as low as –8.5°C at night, are major predisposing factors along with managemental stresses. Vaccination of animals with a homologous PPR vaccine appeared to decrease dramatically the occurrence of the disease, showing that PPR played an important role in the outbreak. Several of the pathogens do not appear to be individually capable of causing the respiratory disease. Appropriate strategies for the prevention of RDC are suggested.     

Genital Disorders,Linear and Testicular Characteristics in Menz Rams

Clinical examination, bodily condition score (BCS), heart girth (HG), body length (BL), wither height (WH), and scrotal circumference (SC) were assessed on 486 mature Ethiopian Menz rams, on small farms, in local markets, and at the main abattoir in Addis Ababa from December 1994 to April 1995. Almost 27% of the rams were found to be unfit for breeding. Poor general condition, mainly in the form of respiratory disorders, was seen in 1.2% of the rams. Balanoposthitis, epididymitis and orchitis were the most common pathological conditions, affecting the external reproductive organs in 14.6%, 4.5% and 4.1% of the rams, respectively. Testicular calcification, cysts and testicular haemorrhagic lesions were detected in 4, 6 and 8, respectively, of the 60 rams examined at necropsy. The BCS, HG, BL and WH averaged 2.1±0.5, 67.7±5.0 cm, 60.1±4.5 cm and 60.1±4.3 cm, respectively. The mean SC was 25.5±3.9 cm and did not vary significantly with age (p>0.05). Among the linear body measurements, the highest correlation was between BL and WH (r = 0.66). SC was found to be most closely correlated to HG (r = 0.46). More investigations into the relationship between the present findings and actual fertility, and on their practical application in the selection of rams for breeding is recommended.     

Pharmacokinetics and microsomal oxidation of praziquantel and its effects on the P450 system in three-month-old lambs infested by Fasciola hepatica

Praziquantel (PZQ) is a broadly effective trematocide and cestocide, widely employed in veterinary and human medicine. In view of several differences in both its pharmacokinetic profile in different animal species and in the cytochrome P450-dependent system between ruminant and nonruminant species, the present study was undertaken to determine the pharmacokinetics of this drug, its effects on the P450 system and the involvement of cytochrome P450 in its metabolism in 3-month-old lambs infested by Fasciola hepatica. Following both oral and i.m. administration, PZQ disposition was best described by a linear one-compartment open model with a rapid absorption and elimination. Although the PZQ dose used by the i.m. route was only half of that used by the oral route, the mean PZQ plasma concentration was higher after i.m. than after oral treatment. Oral treatment with 30 mg/kg/day of PZQ did not modify the mono-oxygenase activities tested, whilst the administration of PZQ at a dose of 60 mg/kg/day for 2 days caused a significant decrease in the P450 3A-dependent erythromycin N-demethylase and 6beta testosterone hydroxylase activities. From the incubation of microsomes from lambs not treated with PZQ, a single metabolite (PZQ 11b-OH or PZQ 1-OH) was identified by GC/MS analysis. By selective inhibition of the 3A subfamily performed with triacetyloleandromycin, the production of this metabolite declined by about 90% suggesting a prominent role of P450 3A isoforms in this oxidation. These features indicate that agents or drugs which are able to modulate P450 3A-dependent catalysis may interfere with the metabolism, bioavailability and therapeutic effects of PZQ.     

An Abattoir Survey on the Frequency of Fatty Liver Syndrome in Dairy Cows from the Suburbs of Tehran

One hundred and six Holstein and Holstein x native cows were inspected before and after slaughter, and liver samples were taken. The fat content of all the liver samples was estimated by an extraction method (Soxhlet). The livers of 29 cows (27%) were classified as fatty. Seventeen of the animals were newly calved, 47 were non-pregnant, 33 were pregnant and 9 were dry, the median values for the fat content of their livers being 60.6, 34.4, 34.7 and 33.8 mg/g, respectively. The median concentration of liver fat in the first group was significantly different from that in each of the other groups (p < 0.01).