Bovine tuberculosis (BTB) is a significant and intractable disease of cattle caused by Mycobacterium bovis. In the UK, despite an aggressive eradication programme, the prevalence of BTB is increasing with an unexplained, exponential rise in cases year on year. Here we show in a study involving 3026 dairy herds in England and Wales that there is a significant negative association between exposure to the common, ubiquitous helminth parasite, Fasciola hepatica and diagnosis of BTB. The magnitude of the single intradermal comparative cervical tuberculin test used to diagnose BTB is reduced in cattle experimentally co-infected with M. bovis and F. hepatica. We estimate an under-ascertainment rate of about one-third (95% Confidence Intervals 27-38%) among our study farms, in the hypothetical situation of no exposure to F. hepatica. This finding may in part explain the continuing spread of BTB and the failure of the current eradication programme in the UK.

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The seroprevalence of Fasciola hepatica infection in a population of commercial dairy herds in England and Wales was estimated using an ELISA that detected antibodies to F hepatica in bulk tank milk. A total of 3130 milk samples, obtained as convenience samples from two commercial milk-testing laboratories, were tested during the winter of 2006/07. Herds considered to be seropositive were categorised as low positive, medium positive or high positive. A geospatial map was drawn to show the distribution of infected herds and the seroprevalence of exposure at regional level, using the Nomenclature of Units for Territorial Statistics boundaries, and at a finer spatial level defined by postcode area. Overall, 76 per cent (95 per cent confidence interval [CI] 74 to 77 per cent) of herds carried antibodies to F hepatica; the seroprevalence in England was 72 per cent (95 per cent CI 70 to 74 per cent) and in Wales it was 84 per cent (95 per cent CI 82 to 86 per cent). The highest prevalences of exposure were found in north-west England, where more than 47 per cent of herds were in the high positive exposure category.

Retrospective testing of 3,232 serum samples from the general population and 518 serum samples from a high-risk group showed no evidence of human exposure to Neospora caninum in England. Results were obtained by using immunofl uorescence antibody testing and ELISA to analyze frequency distribution.T he protozoan parasite Neospora caninum has recently emerged as a major cause of disease in cattle and dogs worldwide (1). An issue of concern is that N. caninum might be zoonotic because of its close biologic relationship to the common zoonotic parasite Toxoplasma gondii and because rhesus monkeys have been experimentally infected (2). Humans could become exposed to N. caninum by accidental ingestion of oocysts shed in the feces of canid defi nitive hosts or following the consumption of raw or inadequately cooked meat that contains tissue cysts. This retrospective study sought immunologic evidence of human exposure to N. caninum in England. Two cohorts of the population were examined: a convenience collection, which approximated the general population, and a putative high-risk group. The StudyThe fi rst cohort comprised anonymized residues of serum samples submitted in 2000 for microbiologic or biochemical testing for diagnostic or screening purposes to 11 laboratories in England that were contributing to the Public Health Laboratories Service (PHLS) Serologic Surveillance Programme (now Health Protection Agency [HPA]) Seroepidemiology Programme (3). The second cohort comprised 518 samples collected in 1995 from the PHLS cohort of farm workers, which was recruited in 1991 to provide annual samples from a population at high risk for zoonotic infections from livestock (4,5). Ethical approval was granted by relevant ethics committees. Serum specimens were initially screened at a dilution of 1:10 in phosphate-buffered saline (PBS), pH 7.2, containing Tween 20 (PBS/Tween) with an inhibition ELISA developed in our laboratory and previously validated in cattle and dogs (6). Positive and negative bovine serum controls were used on each ELISA plate. In the absence of a human positive control, we used a primate serum sample as a further positive control. Optical density was read at 450 nm, and percentage inhibition (PI) values were calculated by using the formula 100 -[(test OD/negative control OD) ×100]. Without specifi c validation, a cut-off of 20% inhibition was chosen to indicate putative positives. This cut-off has been used for previous comparison of the inhibition ELISA with a conventional N. caninum-specific ELISA in bovine sera (6). All samples with inhibition >20% were subsequently tested in an immunofl uorescence antibody test (IFAT) (7) with appropriate species-specifi c fl uorescein isothiocynate conjugates. All samples were tested at a dilution of 1:50 with positive controls of bovine and primate N. caninum serum and bovine negative control serum as above. For the inhibition ELISA results, the distribution of the data was examined fi rst by plotting percent inhibition, with the data aggregated into bands of 10%....