The antibody response of sheep to vaccination against Johne's disease

Extract

Vaccination has been promoted for the control of Johne's disease in sheep. At present vaccination is used especially in merino flocks.     

Cross species transmission of ovine Johne's disease from sheep to cattle: an estimate of prevalence in exposed susceptible cattle

OBJECTIVE: To determine the prevalence of infection of cattle with the sheep strain of Mycobacterium avium subsp paratuberculosis at least two years after exposure at < 6 months old. DESIGN: Prospective survey One thousand seven hundred and seventy-four cattle from 12 properties (Farms A to L) were sampled by ELISA and faecal culture to detect evidence of infection with M a paratuberculosis. All properties had a known history of Johne's disease (JD) in sheep, and sampled cattle were likely to be susceptible to JD at the time they were first exposed, being at an age of 6 months or less. In addition, opportunistic investigations were undertaken of ELISA reactor cattle discovered during testing for the Australian Johne's Disease Market Assurance Program for Cattle (Farms M and N). RESULTS: All animals in the survey gave negative results on serology while one animal from a herd of 349 gave a positive faecal culture result. Follow-up faecal culture, post-mortem and histopathology on the latter animal were negative, suggesting that it was a passive faecal shedder or carrier. Two occurrences of OJD transmission to cattle were detected during the opportunistic investigations. CONCLUSION: These observations confirm existing beliefs about the risk of transmission of OJD to cattle, that the risk of transmission is low. However transmission occurs sporadically. An estimated upper limit of prevalence of S strain M a paratuberculosis infection in susceptible exposed cattle in the OJD high prevalence area of New South Wales is 0.8%, assuming a common prevalence within herds.     

A study of periodontal disease in sheep over a twelve month period

Sheep affected by broken mouth periodontal disease (P.D.) were examined over a twelve month period for different clinical parameters. It is suggested that P.D. in sheep is an episodic phenomenon similar to human P.D., and that only a few animals with signs of P.D. may undergo clinically significant destruction over a yearly period. No single parameter could reliably predict future deterioration in other parameters.     

The impact of malnutrition and other causes of losses of adult sheep in 12 flocks during drought

OBJECTIVE: To establish the range and cost of losses in Merino flocks in southern New South Wales during drought conditions by determining the cause of death, morbidity or wasting in adult sheep. DESIGN AND POPULATION: Pathological studies were performed on 392 dead or moribund adult sheep from 12 Ovine Johne's disease (OJD)-infected flocks during 2002 and a further 58 sheep culled due to wasting from one of these flocks in 2003. Flocks ranged between 3,500 and 20,000 sheep. METHOD: The most likely cause of death, morbidity or wasting was determined following consideration of the environment in which the animal was found, clinical and gross pathological findings, plus histopathology of tissues collected during necropsy. RESULTS: A most likely cause of death, morbidity or wasting was determined for 362 sheep in 2002 and 58 sheep in 2003. OJD contributed to the death of 250 sheep in 2002, and wasting of 48 sheep in 2003. Of the sheep that died or were euthanased due to other causes, malnutrition was a contributing factor in the death of 70 sheep (63%) in 2002 and 2 sheep (20%) in 2003. Losses were not evenly distributed across flocks, with 57% of mortalities caused by malnutrition in 2002 occurring in one flock. Malnutrition accounted for 18% of the annual cost of all deaths among adult sheep in 2002 with an average cost of $16,882 per farm. Losses not attributed to malnutrition included a range of infectious and non-infectious disorders. These included balanoposthitis, clostridial enterotoxaemia, cutaneous myiasis, endoparasitism, enteritis, intestinal adenocarcinoma, misadventure, peritonitis, periparturient death of ewes, photosensitisation, pneumonia, post-shearing stress and squamous cell carcinoma of the perineum. CONCLUSION: Almost one third of mortalities in OJD-infected flocks during drought were unrelated to OJD and could be reduced by improving nutritional and disease management practices. The importance of close supervision of the flock is highlighted so that early management intervention can be instituted, including the culling of cases of welfare concern.     

Epidemiological survey of cestode-larva disease in Greek sheep flocks

The epidemiological status of hydatidosis, cysticercosis, and gid in sheep and the production practices of sheep farmers that increase the risk of exposure of sheep to infecting agents of these diseases were investigated in Thessaly, central Greece during 2002-2006. A total of 700 hoggets (sheep up to the age of 1 year) and 1500 adult sheep were examined randomly at an abattoir survey and the prevalences of hydatidosis and cysticercosis were found 39.32% and 29.41%, respectively. Hoggets had significantly lower prevalences of hydatidosis and cysticercosis compared to adult sheep (p<0.001). The distribution of parasitic cysts showed an overdispersion pattern mostly in the hogget population. The proportion of fertile hydatid cysts was significantly higher in hoggets compared to adult sheep (p<0.001). A cohort of 74 sheep flocks was observed during the same period in a prospective survey to assess the incidence of gid. A total of 57 sheep belonging to 15 flocks (20.27% of investigated flocks) developed clinical signs of gid at an annual rate of 11.40+/-4.77 (95% C.I.). In the infected flocks there were 3.80+/-0.92 (95% C.I.) gid cases per flock. The mean age of onset of clinical signs for all sheep was 11.86+/-1.33 months (95% C.I.) (range 5-22 months) while for hoggets was 8.48+/-0.73 (95% C.I.) (range 5-12 months) and for adult sheep 17.23+/-1.42 (95% C.I.) (range 13-22 months). A significant difference was observed in the prevalence of unilateral blindness between hoggets (31.42%) and adult sheep (4.54%) (p<0.05). The most common production practices identified in a questionnaire survey of sheep farmers that may increase the risk of exposure of sheep to hydatidosis, cysticercosis, and gid were the improper disposal of dead animals, the access of farm dogs to offal of slaughtered sheep, the carelessness of farmers to treat farm dogs with anthelmintics, and the grazing of flocks in fields where stray dogs have free access.     

Increase in the prevalence of Johne's disease in sheep in Scotland

Increased prevalence of Johne's disease in sheep; abomasal damage in young cattle due to ostertagiosis; parasitic gastroenteritis in young sheep due to Nematodirus, Teladorsagia and Chabertia species; Streptococcus suis serotype 2 associated with a range of clinical signs in pigs; respiratory cryptosporidiosis confirmed in wild red grouse. These are among matters discussed in the disease surveillance report for October 2010 from SAC Consulting: Veterinary Services (SAC C VS).     

A preliminary study of possible genetic influences on the susceptibility of sheep to Johne's disease

OBJECTIVE: To investigate possible genetic influences on susceptibility or resistance of sheep to Johne's disease. DESIGN: A field and laboratory study of two fine-wool Merino flocks with a high prevalence of disease due to Mycobacterium avium subsp paratuberculosis infection. PROCEDURE: Adult sheep were phenotypically classified as having severe, mild or no disease on the basis of clinical, pathological and cultural tests for paratuberculosis, and as positive or negative in tests for humoral immunity (agar gel immunodiffusion test) or cell mediated immunity (skin test for delayed type hypersensitivity). Correlations with phenotype were sought for polymorphisms at loci within selected immune function genes (NRAMP, MHC complex, IFN-gamma, lysozyme, leukaemia inhibiting factor). RESULTS: Possible associations of particular NRAMP and MHC alleles with susceptibility or resistance to Johne's disease were detected. CONCLUSION: If the results of this preliminary study are confirmed in further work, then the use of rams with "resistant" genotypes may assist in the control of Johne's disease in infected flocks.     

A longitudinal study to evaluate the diagnostic potential of a direct faecal quantitative PCR test for Johne's disease in sheep

A longitudinal study was carried out to evaluate the diagnostic potential of the previously developed direct faecal real-time quantitative PCR (QPCR) assay (Kawaji et al., 2007) for the detection of Mycobacterium avium subsp. paratuberculosis (MAP) infected sheep. Of the 58 sheep, 38 were orally inoculated with MAP, while 20 controls were maintained separately from the infected group throughout the trial. All animals were tested by QPCR, faecal culture and serum ELISA pre-inoculation and at 4, 8 and 13 months post-inoculation, and were necropsied at 13 months post-inoculation. Eighteen out of 38 inoculated sheep were detected by QPCR to be shedding MAP in faeces at 4 months post-inoculation, while only one sheep was positive in faecal culture at this time point. At 8 months post-inoculation, MAP DNA was detected in faeces of all inoculated sheep by QPCR, while MAP organisms were isolated from only 34% of the inoculated animals by faecal culture. The QPCR results for faecal samples that were collected at necropsy demonstrated that faecal QPCR was more sensitive than culture of intestinal tissues for MAP. The QPCR assay was confirmed to be a sensitive and specific ante-mortem diagnostic test for MAP in sheep, circumventing faecal culture which is a less sensitive and highly time consuming test. Quantification of MAP DNA in faeces by QPCR may provide immediate information to estimate the stage of the infection as well as the risk of transmission from infected animals.     

Colitis in sheep due to a Campylobacter-like bacterium

Epidemic diarrhoea was observed in approximately 2,000 of 6,700 sheep on 9 farms. The disease, called weaner colitis, caused mortality of 1%, while morbidity varied from 20 to 75%. Colon contents from affected sheep were inoculated into 17 sheep, 13 of which developed diarrhoea 5 to 7 days after inoculation. Naturally and experimentally infected sheep had mild, erosive typhlitis and colitis. Microscopic examination of washed scrapings of colonic mucosa from all affected sheep revealed masses of curved bacteria that were not seen in controls. Electron microscopic examination showed similar bacteria adherent to colonic epithelium of an experimentally infected sheep. Curved, motile bacteria were isolated from 2 naturally occurring cases. One isolate was inoculated into 9 sheep, 2 of which developed diarrhoea. The other isolate was given to 4 sheep without observable effect. The curved bacteria grew only on media containing blood, in an atmosphere of approximately 10% air, 10% CO2 and 80% H2. They were Gram-negative, with a polar flagellum at one or both ends, they did not ferment glucose or give a positive catalase reaction. It is suggested that these bacteria are a new Campylobacter species and that they play a major role in the aetiology of weaner colitis.     

Temporal patterns and quantification of excretion of Mycobacterium avium subsp paratuberculosis in sheep with Johne's disease

OBJECTIVES: To determine the frequency of excretion of Mycobacterium avium subsp paratuberculosis in Merino sheep with Johne's disease and to quantify excretion in a group of Merino sheep. DESIGN: A pen and laboratory experiment. PROCEDURE: Seven sheep selected from an affected flock on the basis of acid-fast bacilli in the sheep's faeces were housed and total daily faecal output was collected, weighed and subjected to culture for M avium subsp paratuberculosis. An end-point titration method was used to enumerate viable M avium subsp paratuberculosis in a 15 day pooled sample from five sheep that had acid-fast bacilli in their faeces while housed. RESULTS: Four sheep with subclinical multibacillary Johne's disease excreted M avium subsp paratuberculosis each day for 11 days of cultural observation. A further three sheep were intermittent excreters but lacked other evidence of infection with M avium subsp paratuberculosis. The average number of viable bacteria excreted was 1.09 x 10(8) per gram of faeces while total daily excretion was 8.36 x 10(10) viable M avium subsp paratuberculosis per sheep. Examination of faecal smears stained with Ziehl Neelsen was an unreliable means of assessing daily excretion in individual animals except in those with severe lesions. CONCLUSION: Excretion of M avium subsp paratuberculosis in Merino sheep with multibacillary Johne's disease occurred daily, proving that environmental contamination can be continuous on farms with endemic ovine Johne's disease. Faecal culture is a useful method for detecting infection as it does not appear to be affected by the timing of collection of a sample from sheep with multibacillary disease however, to maximise the sensitivity of disease surveillance using faecal culture, sampling rates should be adjusted to take account of the proportions of multibacillary and paucibacillary cases.     

Losses related to the ingestion of lincomycin-medicated feed in a range sheep flock

Because of an episode of abortion caused by a tetracycline-resistant Campylobacter jejuni, lincomycin was mixed into a barley pellet and fed to 3,000 range ewes at a dosage of 225 mg/ewe/day. After the second feeding, a number of ewes were anorectic and diarrheic, and 6 were dead. Necropsies revealed congestion and hemorrhage of the entire gastrointestinal tract. The feeding of the medicated pellets was discontinued immediately. Sick ewes were treated with antihistamines and corticosteroids, but they did not recover, and many died during the next several weeks. Lambs born within the first 7 days after the incident were alert and vigorous. Dams did not produce milk and many died during or after parturition. Later, however, lambs were born dead or weak, and abortions of autolyzed lambs began. Affected ewes examined 3 weeks later had salmonellosis and/or toxic tubular nephrosis associated with an oxalate-like crystal. The flock had been grazed on range infested with Halogeton glomeratus just before treatment with lincomycin, and it also had a history of Salmonella-related abortions. The deaths finally ceased after a month. Approximately 2,000 ewes and 3,200 lambs were lost, resulting in an economic loss of $550,000.     

A survey on neoplasia in domestic species over a 40-year period from 1935 to 1974 in the Republic of South Africa. II. Tumours occurring in sheep

A survey was carried out on all ovine neoplasms recorded in the registration files of the Section of Pathology of the Veterinary Research Institute at Onderstepoort over a 40-year period from 1935 to 1974. The neoplasms were divided and tabulated into 8 groups according to body systems or tissue types. Out of a total of 673 neoplasms, 436 (64,8%) were cases of jaagsiekte (pulmonary adenomatosis). Of the remaining 237 neoplasms, 41,3% involved the skin. Eighty per cent of the cutaneous neoplasms were squamous cell carcinomas which varied from well-differentiated to anaplastic. The majority occurred on the head, in particular on the ears, frontal region and on the eyelids or nictitating membrane. Several factors have been suggested to explain the high incidence of squamous cell carcinomas on the head. Lymphosarcomas were the 3rd most commonly encountered tumours, whilst a significant number of hepatocellular carcinomas also occurred. A variety of tumours of connective tissue origin were recorded, the most common of which arose from fibrous tissue and cartilage.     

A comparison of whole virus and recombinant transmembrane ELISA and immunodiffusion for detection of ovine lentivirus antibodies in Italian sheep flocks

Sera from two sheep experimentally infected with ovine lentivirus (OLV) and from 186 sheep selected from flocks with known high or low prevalence of infection or on the basis of virological or histopathological examination were simultaneously tested by whole virus (WV) ELISA, recombinant transmembrane (r-TM) ELISA and AGID assay. Antigens for both the WV ELISA and AGID were prepared from an Italian field isolate; recombinant antigen was derived from the N-terminal region of the transmembrane envelope protein of strain K1514. The WV ELISA detected the highest number of seropositives, followed by the r-TM ELISA and AGID test. The sensitivity and specificity of the r-TM ELISA relative to the WV ELISA were 0.66 and 0.95, respectively. Immunoblot analysis of 14 WV ELISA-positive and r-TM ELISA-negative sera showed that the major core protein was immunodominant on WV antigen. It is concluded that the r-TM ELISA was more sensitive than the AGID test but less sensitive that the WV ELISA, particularly for detecting antibodies in the early stages of infection.Abbreviations AGID agar gel immunodiffusion - bp base pair - ELISA enzyme-linked immunosorbent assay - FBS fetal bovine serum - IB immunoblot - kD kilodalton - OLV ovine lentivirus - MEM minimal essential medium - p.i. post-infection - r recombinant - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis - TM transmembrane - WV whole virus     

Epizootic of external and internal abscesses in a large goat herd over a 16-year period

From 1973 through 1988, 518 external and internal abscesses were diagnosed in a large commercial goat herd. Of the 518 abscesses, 238 were primary and 280 were secondary abscesses in the same or other anatomic locations. During this period, the herd varied in size from 94 goats in 1973 to 431 goats in 1988. Abscesses in the jaw area were detected in 141 goats, 4 of which developed osteomyelitis of the mandible. Sternal abscesses were detected in 72 goats, with 2 also having osteomyelitis of the sternum diagnosed at necropsy. Most of the abscesses were in the jaw, sternal, facial, and cervical areas. Lung abscesses were diagnosed at necropsy in 20 goats that most recently had 1 or more superficial abscesses. Abscess incidence was 27.6% (112 of 406) in wethers and 22.9% (154 of 687) in does. Actinomyces pyogenes was isolated most frequently by bacteriologic culture of abscess specimens and about 3 times as often as was Corynebacterium pseudotuberculosis or Staphylococcus sp, usually coagulase-positive S aureus. Bacteriologic culture of blood samples, taken during abscess episodes, yielded A pyogenes (n = 3) or C pseudotuberculosis (n = 1) in 3 goats. Results of antibiotic treatment of abscesses were disappointing, with little evidence of altering the course of the disease or sterilizing the abscess, despite the fact that the bacteria were susceptible in vitro to the antibiotics used. Excision of intact abscesses was the preferred treatment for abscesses of the jaw and facial areas.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characteristics of the spatio-temporal network of cattle movements in France over a 5-year period

A good knowledge of the specificities of the animal trade network is highly valuable to better control pathogen spread on a large regional to transnational scale. Because of their temporal dynamical nature, studying multi-annual datasets is particularly needed to investigate whether structural patterns are stable over the years. In this study, we analysed the French cattle movement network from 2005 to 2009 for different spatial granularities and temporal windows, with the three-fold objective of exploring temporal variations of the main network characteristics, computing proxies for pathogen spread on this network, which accounts for its time-varying properties and identifying specificities related to the main types of animals and farms (dairy versus beef). Network properties did not qualitatively vary among different temporal and spatial granularities. About 40% of the holdings and 80% of the communes were directly interconnected. The width of the aggregation time window barely impacted normalised distributions of indicators. A period of 8–16 weeks would suffice for robust estimation of their main trends, whereas longer periods would provide more details on tails. The dynamic nature of the network could be seen through the small overlap between consecutive networks with 65% of common active nodes for only 3% of common links over 2005–2009. To control pathogen spread on such a network, by reducing the largest strongly connected component by more than 80%, movements should be prevented from 1 to 5% of the holdings with the highest centrality in the previous year network. The analysis of breed-wise and herd-wise subnetworks, dairy, beef and mixed, reveals similar trends in temporal variation of average indicators and their distributions. The link-based backbones of beef subnetworks seem to be more stable over time than those of other subnetworks. At a regional scale, node reachability accounting for time-respecting paths, as proxy of epidemic burden, is greater for a dairy region than for a beef region. This highlights the importance of considering local specificities and temporal dynamics of animal trade networks when evaluating control measures of pathogen spread.