Enzootic abortion of ewes

Aitken, I.D.; Clarkson, MJ; Linklater, KA

doi:10.1136/vr.126.6.136

Cited by 45 publications

(21 citation statements)

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“…However, although inactivated vaccines may reduce the abortion rate, they do not completely prevent bacterial shedding and reproductive failures may still occur (9). In addition, the efficacy of inactivated vaccines is highly variable (9), with reports of occasional EAE outbreaks in vaccinated flocks (22–24). …”

Section: Introductionmentioning

confidence: 99%

Effect of Preventive Chlamydia abortus Vaccination in Offspring Development in Sheep Challenged Experimentally

et al. 2016

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Ovine enzootic abortion, caused by Chlamydia abortus, leads to important economic losses worldwide. In addition to reproductive failures, infection may impact lamb growth during the first weeks after birth, yet this effect has not been well characterized. Vaccination can help to control the disease but variable efficacy values have been described, possibly related with factors associated with the host, the vaccine, the parameter used for efficacy determination, and the challenge conditions. In this context, we evaluated the efficacy of an inactivated standard commercial vaccine and a 1/2 diluted dose in pregnant sheep challenged with C. abortus by examining multiple indicators of vaccine effect (including incidence of reproductive failures, bacterial excretion, and evolution of weight gain of viable lambs during the first month of life). Three groups of ewes [control non-vaccinated, C (n = 18); vaccinated with standard dose, SV (n = 16); and vaccinated with 1/2 dose, DV (n = 17)], were challenged approximately 90 days post-mating and tested using direct PCR (tissue samples and vaginal swabs) and ELISA (serum) until 31 days post-reproductive outcome. There were not significant differences in the proportions of reproductive failures or bacterial shedding after birth/abortion regardless the vaccination protocol. However, a beneficial effect of vaccination on offspring growth was detected in both vaccinated groups compared with the controls, with a mean increase in weight measured at 30 days of life of 1.5 and 2.5 kg (p = 0.056) and an increase in the geometric mean of the daily gain of 8.4 and 9.7% in lambs born from DV and SV ewes compared with controls, respectively. Our results demonstrate the effect of an inactivated vaccine in the development of the offspring of C. abortus-infected ewes at a standard and a diluted dose, an interesting finding given the difficulty in achieving sufficient antigen concentration in the production of enzootic abortion of ewes-commercial vaccines.

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Section: Introductionmentioning

confidence: 99%

Effect of Preventive Chlamydia abortus Vaccination in Offspring Development in Sheep Challenged Experimentally

et al. 2016

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“…The main infectious diseases that cause abortion in sheep and goats are: Brucella melitensis (Darwish and Benkirane, 2001), Brucella ovis (Libal and Kirkbride, 1983), C. abortus (Aitken et al, 1990), Salmonella abortus ovis , Champylobacter foetus (Collins and De Lisle, 1985), Champylobacter jejuni, Toxoplasma gondii (Chanton-Greutmann et al, 2002), Leptospira pomona (Ellis, 1994) and Listeria monocytogenes (Low and Renton, 1985).…”

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confidence: 99%

Seroprevalence of antibodies to chlamydophila abortus shown in awassi sheep and local goats in jordan

Al-Qudah¹,

Sharif²,

Raouf³

et al. 2004

Vet. Med.

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ABSTRACT:A cold complement fixation test (CFT) was used to identify C. abortus infection in ewes and does in northern Jordan. Sera from 36 flocks of sheep and 20 flocks of goats were collected randomly. The results showed that 433 (21.8%) out of 1 984 ovine sera, and 82 (11.4%) out of 721 caprine sera, were seropositive for C. abortus infection, as indicated by a titre ≥ 1:40. However, all the tested sheep flocks and goat flocks (100%) revealed at least one seropositive animal. There was a strong association (P < 0.05) between the rate of C. abortus infection and the size of the sheep flock, when larger flocks had higher infection rates. However, in goats, the flock size had no relationship with seropositivity. Age had no significant (P > 0.05) impact on C. abortus seropositivity. In sheep, there was a significant difference (P < 0.05) between the rates of the chlamydial infection in the four studied areas of northern Jordan. The highest infection rate in sheep (31.2%) was recorded in Mafraq area, while the rates in Irbid, Ajloun and Jerash were 18.5%, 11.2% and 13.9%, respectively. In goats, there was no significant difference between the rates of the chlamydial infection in the two areas studied. The rates of goat infections were 10.8% and 11.8% in Ajloun and Jerash areas, respectively.

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“…Despite the global impact of chlamydial disease, vaccines are available for only two chlamydial species, Chlamydia abortus and Chlamydia felis, which infect ovine and feline species, respectively. A formalin-inactivated vaccine against C. abortus infection, which in the United Kingdom costs the agricultural industry an estimated £20 million each year (2), was developed in the 1960s but did not offer complete protection and required revaccination every 3 years. This vaccine subsequently became demonstrably ineffective when C. abortus infections occurred in vaccinated flocks in the late 1970s (1,14).…”

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Genomic Analysis of an Attenuated Chlamydia abortus Live Vaccine Strain Reveals Defects in Central Metabolism and Surface Proteins

et al. 2009

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Comparative genomic analysis of a wild-type strain of the ovine pathogen Chlamydia abortus and its nitrosoguanidine-induced, temperature-sensitive, virulence-attenuated live vaccine derivative identified 22 single nucleotide polymorphisms unique to the mutant, including nine nonsynonymous mutations, one leading to a truncation of pmpG, which encodes a polymorphic membrane protein, and two intergenic mutations potentially affecting promoter sequences. Other nonsynonymous mutations mapped to a pmpG pseudogene and to predicted coding sequences encoding a putative lipoprotein, a sigma-54-dependent response regulator, a PhoH-like protein, a putative export protein, two tRNA synthetases, and a putative serine hydroxymethyltransferase. One of the intergenic mutations putatively affects transcription of two divergent genes encoding pyruvate kinase and a putative SOS response nuclease, respectively. These observations suggest that the temperature-sensitive phenotype and associated virulence attenuation of the vaccine strain result from disrupted metabolic activity due to altered pyruvate kinase expression and/or alteration in the function of one or more membrane proteins, most notably PmpG and a putative lipoprotein.The Chlamydiaceae represent a group of obligate intracellular bacteria responsible for a wide range of diseases in many different hosts with significant and broad economic and public health impacts. Despite the global impact of chlamydial disease, vaccines are available for only two chlamydial species, Chlamydia abortus and Chlamydia felis, which infect ovine and feline species, respectively. A formalin-inactivated vaccine against C. abortus infection, which in the United Kingdom costs the agricultural industry an estimated £20 million each year (2), was developed in the 1960s but did not offer complete protection and required revaccination every 3 years. This vaccine subsequently became demonstrably ineffective when C. abortus infections occurred in vaccinated flocks in the late 1970s (1, 14). Although inactivated vaccines are still used, more effective C. felis and C. abortus vaccines derived from live attenuated strains are also available. However, C. felis reinfection is not completely controlled with the live attenuated C. felis vaccine, as vaccinated animals still shed chlamydiae (32). In contrast, the live attenuated C. abortus vaccine blocks reinfection and shedding (24, 25).The C. abortus vaccine is based on a live attenuated strain obtained by nitrosoguanidine (NTG) mutagenesis of the virulent strain AB7, isolated from an aborted lamb (8). NTG causes mutations by methylation of nucleotides, especially of guanine, which can then pair with thymine or cytosine (16), giving rise to a GC-to-AT conversion. Other nucleotide substitutions are seen less frequently with deletions resulting from lesion repair. Treatment of AB7 with NTG produced two temperature-sensitive mutants, 1B and 1H, which were attenuated in the mouse model (21). Unlike 1H, which was unstable in temperature-sensitive growth studies, the ...

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Enzootic abortion of ewes

Cited by 45 publications

References 0 publications

Effect of Preventive Chlamydia abortus Vaccination in Offspring Development in Sheep Challenged Experimentally

Effect of Preventive Chlamydia abortus Vaccination in Offspring Development in Sheep Challenged Experimentally

Seroprevalence of antibodies to chlamydophila abortus shown in awassi sheep and local goats in jordan

Genomic Analysis of an Attenuated Chlamydia abortus Live Vaccine Strain Reveals Defects in Central Metabolism and Surface Proteins

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