Serological survey using ELISA to determine the prevalence of Coxiella burnetii infection (Q fever) in sheep and goats in Great Britain.

A survey of Coxiella burnetii infection (Q fever) in sheep flocks and goat herds in Great Britain was undertaken. A total of 5791 sheep (384 flocks) and 522 goats (145 herds) were examined for C. burnetii antibodies using an ELISA. Overall, 53 sheep (37 flocks), and four goats (four herds), tested positive. Estimates of individual animal, between-flock/-herd and within-flock/-herd crude prevalences were 0·9%, 10·2% and 9·0%, respectively, for sheep, and 0·8%, 3% and 26·3%, respectively, for goats. With sheep, the likelihood of an animal testing positive increased with total flock size (P = 0·002) and number of breeding ewes in the flock (P = 0·021). It also increased with number of goats within a 10 km radius (P = 0·038). There was no evidence for spatial clustering of positive herds above that expected by chance alone. No analysis of risk factors was attempted for goats because of the paucity of positives.

Detection of Bovine Leukaemia Virus Antibodies and Proviral DNA in Colostrum Replacers.

Great Britain has been bovine leukaemia virus (BLV) disease free since 1999. We recently reported three separate incidents of BLV seropositivity on farms with home-reared cattle due to the use of colostrum replacer rather than infection with BLV (Emerg. Infect. Dis., 19, 2013, 1027). These cases were all linked via the use of the same brand of colostrum replacer. Here, we investigate further by examining multiple brands of colostrum replacer for proviral DNA and BLV antibodies. BLV antibodies were detected in 7 of the colostrum replacers tested, with PCR concurring in two cases. Thus, the use of these BLV antibody-positive colostrum replacers may also lead to false-positive serological diagnostics.

An investigation into the role of Chlamydophila spp. in bovine upper respiratory tract disease.

An outbreak of upper respiratory tract disease was investigated in a group of 17 housed home-bred calves on a mixed dairy, beef and sheep farm in Devon. Conjunctival swabs were collected and tested for Chlamydophila spp. DNA using a PCR test that detects Chlamydophila abortus and Chlamydophila psittaci. Six of the calves tested gave a positive result. Further epidemiological observations and laboratory testing indicated that the adult dairy cows, from which the affected calves originated, were the most likely source of infection.

Lymphadenopathy and non-suppurative meningo-encephalitis in calves experimentally infected with bovine immunodeficiency-like virus (FL112).

In an experiment on bovine immunodeficiency-like virus (BIV), the virological and serological aspects of which were reported in an earlier paper, three groups (A, B and C) of three calves were inoculated subcutaneously with a recently isolated strain (FL112). For group B and group C, the virus was suspended in milk, and for group C (controls) the viral suspension was subjected to pasteurization before inoculation. The calves were killed for necropsy 12 months later. Clinical assessment revealed subtle ataxia in two group A calves, which took the form of an intermittent "shifting" (from one leg to another) lameness, and palpable enlargement of the pre-scapular lymph nodes in one group B animal. At necropsy, haemal lymph nodes (0.1 to 0.5 cm in diameter), occurring singly, were observed in all animals. However, in groups A and B (but not C), enlarged haemal lymph nodes (< or = 2 cm in diameter) were also seen, occurring singly and in chains; and in one group A animal they occurred in grape-like clusters. In groups A and B (but not C), histopathological examination revealed generalized hyperplastic changes in lymph nodes, especially the haemal lymph nodes. This finding was particularly striking in the two clinically ataxic animals from group A, which also showed a non-suppurative meningo-encephalitis; the latter was possibly the cause of the subtle clinical signs. This study supports previous findings on lymphadenopathy resulting from experimental infection with BIV.

Bovine immunodeficiency-like virus: inactivation in milk by pasteurisation.

Bioassay was used to determine whether bovine immunodeficiency-like virus (BIV) in milk was inactivated by pasteurisation. Three groups of three calves were inoculated with virus (BIV isolate FL112), milk seeded with virus and milk seeded with virus that had been pasteurised before inoculation, respectively. Seroconversion to BIV was monitored for 12 months by an indirect immunofluorescence assay. The presence of BIV proviral DNA in peripheral blood was determined by a nested polymerase chain reaction (PCR). The animals were euthanized and virus isolation and PCR were attempted on peripheral blood mononunclear cells, prescapular lymph node and spleen. Transmission of BIV was confirmed in the groups that were inoculated with the virus and with the virus in milk, but no evidence of its transmission was demonstrated in the group that received the pasteurised inoculum.

Serological diagnosis of ovine enzootic abortion by comparative inclusion immunofluorescence assay, recombinant lipopolysaccharide enzyme-linked immunosorbent assay, and complement fixation test.

Since the 1950s, serological diagnosis of ovine enzootic abortion (OEA), caused by strains of Chlamydia psittaci, has been based mainly on the complement fixation test (CFT), which is neither particularly sensitive nor specific since antibodies to other chlamydial and enterobacterial pathogens may be detected. In this study. a recombinant enzyme-linked immunosorbent assay (rELISA) (medac, Hamburg, Germany), based on a unique chlamydial genus-specific epitope of Chlamydia trachomatis L2 lipopolysaccharide, was evaluated for sensitivity and specificity as a primary screening assay for OEA by comparison with the CFT. A comparative inclusion immunofluorescence assay (IFA), in which antibody titers to C. psittaci and Chlamydia pecorum were examined, was used as the reference test for 573 serum samples from four flocks. Reactivity to C. pecorum was measured since inapparent intestinal infections by C. pecorum are believed to be common in British flocks. In detecting positive sera from an abortion-affected flock, in which a C. pecorum infection was also suggested by IFA, the rELISA outperformed the CFT with significant evidence for increased sensitivity (P = 0.003). In two flocks in which C. pecorum infections alone were suggested by IFA, the rELISA and CFT were prone to detect low levels of false-positive results, but the values were not significant. The rELISA provided results in one flock in which sera that were anticomplementary could not be resolved by the CFT. In another flock in which abortion had not occurred but infection by both chlamydial species was suspected, no significant difference was found between the sensitivities of the rELISA and CFT. The rELISA could not differentiate ovine C. psittaci and C. pecorum infections but was shown to be a more sensitive primary screening test for OEA than was the CFT, particularly where abortion had occurred and even when antibodies due to additional inapparent infection(s) by C. pecorum were present.