Comparison of five tests for the detection of antibodies against chlamydial (enzootic) abortion of ewes

Abstract

Five tests for antibodies against chlamydial (enzootic) abortion of ewes were compared using 255 sera from experimentally (group 1) or naturally (group 2) infected animals, flocks free of the disease (group 3) and individual animals testing positively by the complement fixation test but from flocks with no evidence of chlamydial abortion (group 4). Sera from five specific pathogen-free lambs vaccinated with two different subtypes of Chlamydia pecorum were also included (group 5). All tests used some form of processed culture of C psitiaci as antigen. Specificities, established with group 3 and 4 sera, ranged between 96 per cent (ELISA using lipopolysaccharide antigen) and 59 per cent (Immunocomb). Reactions with group 5 sera suggested that the cause of false positive results in the field might be cross-reactive antibodies against the arthritogenic subtype of C pecorum. Sensitivities, established with groups 1 and 2 sera, ranged between 81 per cent (Immunocomb) and 51 per cent (ELISA using solubilised protein antigen). The minimum sample sizes required to be 95 per cent certain of detecting at least five seropositives in two infected flocks (combined data) were 15 to 48, dependent on the test applied. The Western blot test, applied to a proportion of samples, yielded no false positives with group 3 sera but 31.7 per cent with group 4 sera. Thus, none of the tests in this comparison emerged as sufficiently satisfactory in all respects, suggesting that further improvements in chlamydial serology must come through the use of non-native antigens or in the form of a competitive ELISA.

Serological Diagnosis of Ovine Enzootic Abortion by Enzyme-Linked Immunosorbent Assay with a Recombinant Protein Fragment of the Polymorphic Outer Membrane Protein POMP90 ofChlamydophila abortus

“…Although it has been reported that the CFT antibody titers are low in these apparently healthy sheep (31,37), in this study both the experimentally infected (group 3) and naturally infected (group 6) animals were found to be negative. This suggests that the lack of specificity of CFT in the field may be due to the arthritogenic and conjunctival subtypes rather than the more common enteric subtype, as suggested previously (19,22). CFT also performed better than has been reported by other groups, in which the sensitivity has been reported to be lower with either naturally or experimentally infected sheep (5,19,25), although six borderline positive samples and two negative samples were obtained from ewes that either aborted or lambed with heavily infected placentas (group 1A).…”

“…This suggests that the lack of specificity of CFT in the field may be due to the arthritogenic and conjunctival subtypes rather than the more common enteric subtype, as suggested previously (19,22). CFT also performed better than has been reported by other groups, in which the sensitivity has been reported to be lower with either naturally or experimentally infected sheep (5,19,25), although six borderline positive samples and two negative samples were obtained from ewes that either aborted or lambed with heavily infected placentas (group 1A). The specificity of CFT and the variability of CFT antibody titers, in which very low or borderline titers are produced in some animals following abortion, reinforce the arguments that the test should be used only for flocks and not for the diagnosis of infection in individual animals (30).…”

“…Group 3 consisted of samples from nine specific-pathogen-free (SPF) lambs, three of which had been immunized with C. pecorum isolate P787 (an ovine arthritogenic isolate), two of which had been immunized with C. pecorum isolate 84-796 (an ovine conjunctival isolate), and four of which had been immunized with C. pecorum isolate 84-604 or W73 (ovine enteric isolates). The animals were immunized as described by Jones et al (19). Group 4 comprised 38 field samples from a flock of ewes from Scotland in which there was clinical evidence of abortion.…”

Alpine ibex (Capra i. ibex) is not a reservoir for chlamydial infections of domestic ruminants and humans

“…It was shown that females with high antibody-titers against Salmonella underwent a decrease in their reproductive success, while antibody-titers against Chlamydophila and Coxiella were not related to the reproductive success of female chamois (Pioz et al, 2008b). The CFT used in the above mentioned studies is of inferior sensitivity and specificity and cross-reactivity to other species of the family Chlamydiaceae is well known (Markey et al, 1993;Donn et al, 1997;Jones et al, 1997;Rodolakis et al, 1998). Thus, false positive results due to cross-reaction with C.…”

Antibody Responses to Recombinant Protein Fragments of the Major Outer Membrane Protein and Polymorphic Outer Membrane Protein POMP90 inChlamydophila abortus-Infected Pregnant Sheep

“…In the United Kingdom and elsewhere, the CFT is used by national veterinary laboratories to screen and accredit sheep and goats as being EAE free. However, the CFT can be insensitive and lacks specificity (20,26). In particular, antigenic cross-reactivity with C. pecorum, as well as with other gram-negative bacteria, such as Acinetobacter spp., complicates the interpretation of results.…”