Epidemiological studies of pig diseases: 1. Use of French protocols for risk factor assessment to predict the health status of Australian herds.

OBJECTIVE: To determine in Australian pig herds the accuracy of French protocols for risk factor assessment. PROCEDURE: Data on health indicators and risk factors were collected for three syndromes, 'pre-weaning diarrhoea', 'post-weaning diarrhoea' and 'respiratory problems', using the French protocols. The protocols were used on 118 occasions in 32 Western Australian pig herds during 3 years (1988 to 1991). RESULTS: There was a wide variation in pre-weaning performance, for example growth rate was 107 to 273 g/day (< 200 g/day in 33% of herds). Respiratory lesions at weaning were associated with poor pre-weaning performance. Post-weaning (21 days after weaning) growth rate was 114 to 408 g/day (< 250 g/day in 54% of herds). In the grower herds, 91% of herds had pneumonia, and growth rate was 439 to 625 g/day (< 550 g/day in 54% of herds). Pleurisy as well as pneumonia was associated with reduced growth rate. The risk factor most closely associated with respiratory health status was air volume per pig. CONCLUSION: Risk factors were most accurate at predicting the health status in post-weaning problems. A weaning weight of at least 7.9 kg and weaning age of 30 days optimised weaner performance. Stocking densities and shed designs providing at least 3 m3 air volume and 0.6 m2 floor space per pig throughout the growing phase should be considered for an improved respiratory health status. Australian pig sheds often do not provide a satisfactory environment for optimum health. The technique of risk factor assessment as an aid to the maintenance of health in pig herds is applicable in Australia, but further research is necessary to determine the most important Australian risk factors.

Epidemiological studies of pig diseases: 2. Post-weaning diarrhoea and performance in Western Australian pigs.

OBJECTIVE: To determine in Australian pig herds the accuracy of French protocols for risk factor assessment of post-weaning diarrhoea and illthrift. PROCEDURE: French protocols for the collection of data on health indicators and risk factors for post-weaning diarrhoea were conducted on 54 batches of weaner pigs from 28 Western Australian pig herds during three years. RESULTS: Large variations in post-weaning performance were found. About one-third of the batches were growing at < 200 g/day during the 3 weeks after weaning, and 54% had growth rates of < 250 g/day. Weaning age and weight of at least 30 days and 7.9 kg, respectively, optimised weaner performance. Other risk factors associated with little post-weaning diarrhoea and good weaner performance were high creep feed intakes, relatively little diarrhoea as suckers, and, contrary to expectations, large temperature fluctuations. CONCLUSION: Overall, the 'predictability' of post-weaning problems as assessed by measurement of risk status, was good. However, the model was less accurate at predicting the performance of a single batch of pigs.

Immunoglobulin isotype of specific antibodies in reproductive tract secretions and sera in Tritrichomonas foetus-infected heifers.

Four virgin heifers were experimentally inoculated intravaginally with 7 x 10(6) Tritrichomonas foetus, and 2 heifers served as uninfected controls. The durations of infection were 13, 20, 21, and 28 weeks, respectively. An ELISA that used whole T foetus antigen was used to detect anti-T foetus immunoglobulins (IgA, IgG1, IgG2, and IgM) in vaginal, cervical, and uterine secretions, and sera during the course of infection. The vaginal and cervical antibody responses were characterized by significantly increased T foetus-specific IgA and IgG1 at 7 to 9 weeks of infection, whereas uterine IgA and IgG1 responses peaked at 10 to 12 weeks. The antibody response in serum was predominantly of the IgG1 and IgG2 subclasses. In all reproductive tract regions, IgA persisted at least until the time of T foetus clearance, and usually longer. The next most persistent isotype was IgG1, lasting longest in the vagina, then cervix, and for the shortest time in the uterus. In local secretions, IgG2 was seen only transiently, increasing at weeks 13 to 15 in the vagina, and at weeks 10 to 12 in the cervix. Little IgM, relative to that present before infection, was detected in any secretion or serum, although cervical secretions had the greatest amount. Eight to 12 weeks after clearance, the 4 experimental heifers were inoculated intravaginally with 1 x 10(5) T foetus; transient infections (2 to 3 weeks' duration) were established in only 2 of 4 heifers, as determined by culturing of reproductive tract secretions.(ABSTRACT TRUNCATED AT 250 WORDS)

Induced Tritrichomonas foetus infection in beef heifers.

Four virgin beef heifers were inoculated intravaginally with 7 x 10(6) Tritrichomonas foetus organisms. Protozoal colonization of the vagina, cervix, and uterus developed within the first week after inoculation. Protozoa were no longer detected in secretions from these regions at approximately the same time in each heifer. Trichomonads were detected in reproductive tract secretions for 13 to 28 weeks. Eight weeks after clearance of trichomonads from the reproductive tract, a second infection was established in 2 of the 4 heifers by intravaginal inoculation of T foetus. The second infections were maintained for up to 4 weeks. The diagnostic sensitivity of wet-mount examination of the reproductive tract secretions was 30%, compared with 78% for culture of trichomonads in secretions. Collection and culturing of specimens of cervical and vaginal mucus provided the most reliable method for diagnosis of trichomoniasis during induced infection of heifers.

Bovine trichomoniasis.

Although virtually unknown in Europe since the widespread adoption of artificial insemination (AI), infection by the sexually transmitted protozoan parasite Tritrichomonas foetus (Fig. 1) results in substantial economic losses throughout the major cattle-rearing areas of the world where natural breeding is relied upon. Infection by T. foetus is increasingly recognized as a significant cause of bovine infertility. In this review, Alex Yule, Susan Skirrow and Robert BonDurant summarize the current knowledge of bovine trichomoniasis and the problems of diagnosis and control of this economically important disease.

Development and preliminary assessment of a polyclonal antibody-based enzyme immunoassay for the detection of Tritrichomonas foetus antigen in breeding cattle.

More sensitive tests are required for the diagnosis of Tritrichomonas foetus infection in cattle and an antigen-detecting enzyme immunoassay (EIA) has been applied to this purpose. An affinity purified immunoglobulin fraction obtained from rabbits immunised with cultured T. foetus served as both capture antibody and as biotinylated indicator antibody. While highly sensitive in the detection of antigen derived from cultured organisms, the assay showed poor sensitivity in the detection of antigen in the cervico-vaginal mucus of artificially infected heifers, with only 75% of culture-positive samples being considered positive for antigen. In a direct comparison, 23/122 samples from a naturally infected dairy herd gave positive cultures, while only 10/122 samples were considered antigen positive by EIA.

Epidemiologic and economic analyses of an unusually long epizootic of trichomoniasis in a large California dairy herd.

An epizootic of trichomoniasis in a large California dairy herd caused an estimated economic loss of $66,538 ($665/infected cow). Greatest losses were caused by infertility (about 50% of losses caused by excess days open). The disease continued in the herd, despite culling older bulls and replacing them with young uninfected bulls and despite institution of an artificial insemination (AI) breeding program for 2 high-production strings. The AI breeder's practice of checking for estrus by vaginal examination was implicated in the spread of the disease. Of 5 cows that became infected before or at conception, 1 had the infection throughout the gestation period and into the next lactation. The prevalence of trichomoniasis in the herd (estimated on the basis of culture results) was 10.67%. The culture method had a calculated sensitivity of only 58.7%. Of 940 cows in the herd, 132 aborted during the epizootic (8 aborted twice); 45 abortions would have been expected in a dairy herd of this size in the absence of trichomoniasis. In high-density mass-bred herds, conditions and/or management practices may be conducive for trichomoniasis transmission, and generally recommended control programs should be adjusted on such dairies. In particular, dairy operators should not assume that culling older bulls and replacing them with young uninfected bulls and that institution of an AI program will be effective in limiting the spread of the disease. Moreover, a diagnostic test with improved sensitivity would greatly assist in the identification of infected cows.

Zinc toxicity in ruminants.

Four natural occurrences of zinc toxicity in sheep and one in calves were studied. To assist in the confirmation of a diagnosis of zinc toxicity, 2 experiments were conducted in which sheep were given toxic amounts of zinc. The clinical findings, clinical pathology, and gross and microscopic pathology are given. Clinical manifestations included inappetance, loss of condition, diarrhoea with dehydration or subcutaneous oedema, profound weakness and jaundice. Significant rises in the concentration of zinc were usually found in the liver, kidney and pancreas, but occasionally in only 1 or 2 of these organs. Many affected sheep were anaemic. Pathological changes were found in the pancreas, kidney, liver, rumen, abomasum, small intestine and adrenal gland. Lesions in the kidney and abomasum apparently made the most significant contribution to the deterioration in health of affected animals, but the pancreas was the only organ consistently affected. The degenerative changes in the pancreas were mainly restricted to the exocrine portion of the organ, and regeneration of the damaged tissue was observed although exposure to toxic amounts of zinc continued. Attention is drawn to the importance of the pancreas in the diagnosis of zinc toxicity and in estimating the period of exposure.

Hemimelia and low marking percentage in a flock of Merino ewes and lambs.

Hemimelia at a prevalence of 11% of lambs marked, and low marking percentage (51%) was observed in a flock of mixed age Merino ewes and their lambs. Hemimelia occurred in one or 2 limbs of affected lambs. Lambs from other flocks on the farm were unaffected, and the condition was not reported from other farms. The condition had not occurred in the past, and has not recurred. No infectious or hereditary factors were implicated in the aetiology of the condition. Grazing Western Australian Blue Lupin stubble by the affected flock during and after joining was the only known difference between this flock and others on the farm.