Borna disease virus and mental health: a cross-sectional study

BACKGROUND

Borna disease is an infectious neurological disease of horses, sheep and possibly other animals. A role for Borna disease virus (BDV) in human neurological and psychiatric illness has been proposed, but this hypothesis remains controversial.

AIM

To investigate the epidemiology of BDV in UK farming communities.

DESIGN

Retrospective cohort study.

METHODS

We measured the seroprevalence of BDV in the PHLS Farm Cohort, a representative sample of those employed in agriculture in the UK, and investigated the clinical significance of our findings by comparing the prevalence of symptoms of neurotic psychopathology in those found seropositive and seronegative.

RESULTS

Seroprevalence was 2.3% (95%CI 1.3- 4.0%) in 1994, 3.1% in 1996 (95%CI 1.9-5.0%) and 2.6% in 1999 (95%CI 1.5%-4.6%). Those living or working on livestock farms had higher seroprevalence (2.6%) than those on mixed (2.3%) or arable (1.6%) farms, but this was not statistically significant. Exposure to horses, sheep and cats did not increase risk of seropositivity. Seropositives were no more likely to report symptoms of psychiatric morbidity.

DISCUSSION

UK farming populations appear to be exposed to Borna disease virus. However, we found no evidence that exposure to BDV was associated with morbidity in this healthy occupational cohort.

Mental health of British farmers

AIMS

To estimate the prevalence of neurotic symptoms in a sample of British farmers, to investigate whether farming characteristics are associated with psychiatric morbidity, and to test the hypothesis that British farmers have a higher prevalence of depression and thoughts of life not worth living than the British household population.

METHODS

A total of 425 farmers from Hereford, Norwich, and Preston completed the Revised Clinical Interview Schedule (CIS-R) by computer between March and July 1999. The comparison cohort consisted of 9830 private householders aged 16-64 from the Office of Population Censuses and Surveys National Psychiatric Morbidity Surveys of Great Britain carried out in 1993 in which the CIS-R was administered. All analyses used the commands developed specifically for survey data available in Stata version 6.0.

RESULTS

Taking a threshold of an overall score of 12 or more on the CIS-R, only 6% of farmers reported clinically relevant psychiatric morbidity. Psychiatric morbidity was not significantly associated with farm type or size in this study. Farmers reported a lower prevalence of psychiatric morbidity than the general population but were more likely to report thinking that life is not worth living, particularly after the low prevalence of psychiatric morbidity had been taken into account (odds ratio 2.56, 95% CI 1.39 to 4.69). When restricting the comparison to only rural or semirural householders, this increased risk was even more pronounced (odds ratio 3.26, 95% CI 1.51 to 7.02).

CONCLUSIONS

The relation between depression and suicidal ideation seems to be quite different among farmers and the general population and warrants further investigation. We have shown it is possible to measure mental health systematically in a sample of British farmers. This study should be repeated in the aftermath of the foot and mouth crisis.

Evidence of persisting serum antibodies to Escherichia coli O157 lipopolysaccharide and Verocytotoxin in members of rural communities in England

The techniques of enzyme-linked immunosorbent assay (ELISA) and immunoblotting were used to examine a total of 1667 sera, from apparently healthy members of rural communities in England, for antibodies to the lipopolysaccharide (LPS) of Escherichia coli O157 and Verocytotoxins (VT). Twenty-nine sera from 22 individuals were shown to have antibodies specific for E. coli O157 LPS. Some of these lived on livestock farms and had occupational contact with cattle, suggesting that personnel working with farm animals may produce serum antibodies to the O157 LPS antigens. Fifteen people had IgG class antibodies to O157 LPS, suggesting long-term exposure to E. coli O157 and five people had serum antibodies on more than one occasion showing evidence of persistent antibodies to O157 LPS. Thirteen sera from 12 of 22 individuals also contained antibodies to VT1, VT2 or both toxins. Ten sera contained antibodies to VT1 and VT2, three sera contained antibodies to VT2 only.

Orf (contagious pustular dermatitis) in farmworkers: prevalence and risk factors in three areas of England

Orf is a zoonotic skin disease which is commonly self-diagnosed by those who tend sheep and goats. This paper reports the prevalence, incidence and risk factors associated with the infection in a cohort of farmworkers from three areas of England, derived from the results of self-reporting and serology. Twenty-three per cent of those employed or living on a sheep farm reported ever having had orf, and the antibody serological profiles indicated a prevalence of 4 per cent and an annual incidence of 2.8 per cen. The main risk factors associated with the infection were contact with sheep, the size of the sheep flock, and contact with dogs.

Low rates of ehrlichiosis and Lyme borreliosis in English farmworkers

To determine the occupational significance of tick-borne zoonoses we sought serological evidence of Lyme borreliosis, human monocytic ehrlichiosis (HME) and human granulocytic ehrlichiosis (HGE) in a representative sample of farmworkers. Although around 20% reported ticks on their domestic and companion animals, few (< 2% per year) reported being bitten by ticks. Seroprevalence of Lyme borreliosis (0.2%), HME (0.2%) and HGE (1.5%) was low. Those seropositive for HGE were no more likely to report tick bites nor more likely to report ticks on their animals. This study provides evidence that farmworkers in England are exposed to tick-borne zoonoses but that they are uncommon. Since the severity of these diseases is linked to delays in diagnosis and treatment, clinicians should be aware of these diagnoses in patients from rural communities, with or without a self-reported history of tick bite.

The risk of acquiring Q fever on farms: a seroepidemiological study

OBJECTIVES

To determine the occupational risk of Q fever.

DESIGN

Cohort study.

SETTING

Community: five English local authority districts.

SUBJECTS AND METHODS

Prevalence and incidence of immunoglobulin G (IgG) specific antibody to Coxiella burnetii phase II antigen was measured in a representative (study) cohort of farm workers in the United Kingdom, and detailed exposure data were collected. Also seroprevalence of Q fever in a (control) cohort of police and emergency service personnel was measured.

RESULTS

Prevalence was significantly (P < 0.01) higher in the study cohort (105/385 v 43/395). During the first 12 month period after enrollment no seroconversions were found (upper 95% confidence limit: 1318/100,000/year). During the second 12 month period after enrollment two seroconversions were found, equalling an incidence of 813/100,000/year (95% confidence interval (95% CI) 98-2937/100,000/year). No association was found between seroprevalence and age. In the study cohort, extent of total contact with farm animals seemed more important than exposure to any specific animal: full time employees were more than four times more likely to be antibody positive than part time employees (P < 0.05). Exposure to cattle, but not sheep, goats, cats, raw milk, and hay (all reported sources of Q fever) was associated with being positive to Coxiella burnetii IgG by univariate analysis but this association was not independent of total farm animal contact.

CONCLUSIONS

The risk of Q fever on livestock farms is related to contact with the farm environment rather than any specific animal exposure. The absence of an increasing prevalence with age suggests that exposure may occur as clusters in space and time (outbreaks).

Zoonotic illness--determining risks and measuring effects: association between current animal exposure and a history of illness in a well characterised rural population in the UK

STUDY OBJECTIVES

To recruit a representative sample of farmworkers, accurately quantify the range and extent of their animal exposures, and measure the associated risks of illness.

DESIGN

Inception cohort.

SETTING

The study was undertaken among farmworkers living in five local authority areas in the catchment of Hereford and Preston Public Health Laboratories, England.

PARTICIPANTS

A quota sample of 404 people on 255 agricultural holdings took part. The holdings were selected at random from the Ministry of Agriculture, Fisheries and Food register. Altogether 58% of eligible subjects approached agreed to participate.

MEASUREMENTS AND MAIN RESULTS

The sample had the same sex distribution as the 1991 census for those giving their occupation as agriculture. The mean age was significantly (p < 0.01) higher (44.6 years v 42.2 years) than that of those giving their occupation as agriculture, forestry or fishing in the census, although the modal range (45-59 years) was the same. At enrollment interviews, subjects individually reported contact with up to nine animal species (mode 4) out of 26 reported in all. Based on the numbers contacted and the frequency and intimacy of contact, scores on a ranked ordinal scale from 0-5 were constructed for each species and frequencies for each score were plotted. Subjects also reported past operations and serious illness. A history of pneumonia was significantly (p < 0.05) associated with a pigeon loft on the farm (relative risk (RR) 7.3) and attending farrowing pigs (RR 6.6), and one of leptospirosis with a rat problem on the farm (RR 28.1). Cattle contact was associated with a significantly lower likelihood (protective) of glandular fever (RR 0.19) and rheumatic or scarlet fever (RR 0.12). These effects were significantly related to rankings of the extent of exposure.

CONCLUSIONS

It is possible to recruit a representative sample of farmworkers and measure their animal exposures in great detail. Among these exposures, associations with plausible risk factors for pneumonia and leptospirosis and apparently protective factors for glandular fever, scarlet fever, and rheumatic fever have been demonstrated, which further show a relationship between the extent of exposure and response. These findings can be tested further by examining the relationship of exposures to serological evidence of illness or by further prospective follow up of this and similarly well characterised cohorts, or both.