Infected Sheep Flocks Research Articles

Bluetongue Virus Infection in Farm Dogs Exposed to an Infected Sheep Flock in South Africa

Bluetongue Virus Infection in Farm Dogs Exposed to an Infected Sheep Flock in South Africa

Humoral immune response to Q fever vaccination of three sheep flocks naturally pre-infected with Coxiella burnetii

Qfever is a zoonotic disease caused by the bacterium Coxiella burnetii; Coxiella-infected ruminants are the main reservoir shedding the pathogen during abortion or parturition through birth products. Germany has a long history of small-scale Q fever epidemics in the human population mostly associated with lambing sheep. Therefore, fast and efficient control measures are essentially required to prevent transmission from infected sheep flocks to humans. In our present study, three sheep flocks were vaccinated with an inactivated C.burnetii phase I vaccine after a field infection with C.burnetii was diagnosed. Serum samples and vaginal swabs were collected at different time points to evaluate the extent of the outbreak and the consequences of the vaccination. The serum samples were examined by phase-specific IgG phase I and phase II ELISAs and a commercial ELISA, simultaneously detecting both phase variations. Moreover, vaginal swabs were analysed by qPCR. The fourth flock with no Q fever history and non-vaccinated animals were used as a control group to evaluate the phase-specific ELISAs. The inactivated C.burnetii phase I vaccine induced an IgG phase II response and boosted the humoral immune reaction against natural pre-infections. Furthermore, the longevity of vaccine-induced antibodies seems to depend on previous infections. Around 16 months after primary vaccination, mainly IgG phase I antibodies were detectable. Vaccination did not prevent shedding at the next lambing season. Most interestingly, the phase-specific ELISAs revealed more C.burnetii positive animals than the blended ELISA-Assay. Taken together, phase-specific ELISAs are suitable tools to provide insights into natural- or vaccine-induced humoral immune responses to C.burnetii in sheep.

Comparative efficacy of five anthelmintic drugs against a naturally acquired Fasciola species infection in sheep in Jumla, Nepal

Fascioliasis is one of the important parasitic diseases in tropical and subtropical countries which limit productivity of ruminants. The aim of present study was to evaluate the efficacy of five different anthelmintics against liver fluke in a naturally infected sheep flock at Sheep and Goat Research Program, Guthichaur, Jumla. Altogether 30 sheep positive with Fasciola eggs were selected for the study. These 30 sheep were divided into six groups including control one and each group consisted five animals. Sheep of Group I, II, III, IV and V were treated with different anthelmintics viz. Albendazole, rafoxanide, oxyclozanide, oxyclozanide and levamisole combination, and triclabendazole respectively. Faecal samples were obtained from each animal per rectum on the day of treatment and again 1, 3, 7, 14 and 28 days post-treatment. The efficacy of the used anthelmintics was determined by faecal egg count reduction percent in which the fecal egg was investigated by sedimentation technique. The results for oxyclozanide, oxyclozanide and levamisole combination and triclabendazole indicated that these drugs were highly effective with faecal egg count being reduced by 100% by day 14 post-treatment. However, the results for albendazole and rafoxanide groups yielded lower efficacy levels, with faecal egg count reductions 92.8% and 91.8% respectively, over the period 28 days post-treatment. These results are highly indicative for albendazole and rafoxanide resistant Fasciola in sheep on this farm.

Monitoring Coxiella burnetii Infection in Naturally Infected Dairy Sheep Flocks Throughout Four Lambing Seasons and Investigation of Viable Bacteria

Progression of Coxiella burnetii infection in four naturally infected sheep flocks, and in their farm environment, was monitored throughout four lambing seasons. Flocks with an active infection were selected based on the presence of C. burnetii DNA in bulk-tank milk (BTM) and a high seroprevalence in yearlings during the previous milking period (Spring 2015). During four consecutive lambing seasons (2015/16–2018/19), samples were collected within 1 week after each lambing period from animals (vaginal swabs, milk and feces from ewes, and yearlings) and the environment (dust indoor sheep premises). BTM samples and aerosols (outdoors and indoors) were monthly collected between lambing and the end of milking. Real-time PCR analyses showed different trends in C. burnetii shedding in the flocks, with a general progressive decrease in bacterial shedding throughout the years, interrupted in three flocks by peaks of reinfection associated with specific management practices. A significant relationship was found between C. burnetii fecal shedding and the bacterial burden detected in dust, whereas shedding by vaginal route affected the detection of C. burnetii in indoor aerosols. Three genotypes were identified: SNP8 (three flocks, 52.9% of the samples), SNP1 (two flocks, 44.8% samples), and SNP5 (one flock, two environmental samples). Coxiella burnetii viability in dust measured by culture in Vero cells was demonstrated in two of the flocks, even during the fourth lambing season. The results showed that infection can remain active for over 5 years if effective control and biosafety measures are not correctly implemented.

Anthelmintic resistance in naturally infected sheep flocks of Cuddalore district, Tamil nadu

Anthelmintic resistance in naturally infected sheep flocks of Cuddalore district, Tamil nadu

Transmission of caprine arthritis encephalitis virus between sheep

ABSTRACT: This study was conducted to evaluate caprine arthritis encephalitis virus (CAEV) transmission among sheep using 15 lambs that were distributed in 2 experimental groups. The exposed group consisted of 10 lambs that remained with their mothers, who were experimentally infected with CAEV. The non-exposed group was characterized as the control group and was comprised of 5 lambs that remained with their CAEV-negative mothers. Blood samples were collected monthly from birth until 1 year of life. To evaluate the transmission, an agar gel immunodiffusion test (AGID), enzyme immunoassay (ELISA), immunoblotting (IB), and nested polymerase chain reaction (nPCR) techniques were used. The non-exposed group was negative in all of the tests throughout the whole experiment. In the exposed group, 2 individuals had positive nPCR results. Positive nPCR samples were sequenced for comparison with the original goat strains and were shown to be similar to the CAEV-Cork strain. Seroconversion was not detected, and clinical manifestations were not observed. Thus, after 1 year of observation, it was verified that CAEV transmission among sheep is possible; however, with discreet frequency. This was an initial study, and other experiments are needed to analyze the adaptive capacity of the CAEV to remain in an infected sheep flock and cause the disease.

Epidemiology of gastrointestinal parasites and impact of two anthelmintic treatment systems in sheep flocks of arid and semi-arid Rajasthan

Comparative epidemiology of gastrointestinal (GI) parasites and economic impact of two anthelmintic treatment systems (conventional and modified) in naturally infected sheep flocks were studied in arid and semi-arid Rajasthan. From April 2004 to March 2016, sheep flocks (376) were evaluated for GI parasites by examining 79311 faecal samples and monitored for performance in two anthelmintic treatment systems. Period from July to mid-September in arid and from early-June to mid-September in semi-arid Rajasthan was found suitable for translation of predominant GI nematode (Haemonchus contortus). The monthly incidence of strongyle nematodes showed almost similar trend among flocks given either modified (1 drench/yr) or conventional (2–3 drenches/yr) anthelmintic treatment. Significantly (P < 0.001) higher pasture larval burden was recorded during July to September in both the regions. Among other GI parasites, only infection with amphistomes was found endemic particularly in semi-arid region. The economic appraisal showed that reduced anthelmintic frequency in modified system as against conventional system had no adverse effect on flock performance. It was concluded that modified anthelmintic intervention provides better opportunities for gainful interaction between epidemiology, weather and management of flocks for worm control and prevent unwanted expenditure incurred by farmer on anthelmintics.

Epizootiological. Study of sheep and goat abortion by Salmonella abortus ovis in Greece

The epizootiological data concerning sheep and goat abortion cases were studied between 1980-1989. The abortion cases were investigated by cultural or serological exaninations. From the affected flocks, where abortions took place, 1.69% to 19.35% were considered as infected by Salmonella abortus ovis SAO after isolation of the organism. The serological examinations of flocks with abortions, revealed a positivity to SAO of 2.7% to 47%. The infected sheep flocks, that were ascertained by isolation of SAO prevailed against the corrensponding goat herds with an average of 11.25% to 6% respectively.

Live Cell Therapy as Potential Risk Factor for Q Fever.

During an outbreak of Q fever in Germany, we identified an infected sheep flock from which animals were routinely used as a source for life cell therapy (LCT), the injection of fetal cells or cell extracts from sheep into humans. Q fever developed in 7 LCT recipients from Canada, Germany, and the United States.

Coxiella burnetii Circulation in a Naturally Infected Flock of Sheep: Individual Follow-Up of Antibodies in Serum and Milk.

The control of Q fever, a zoonotic disease caused by the Coxiella burnetii bacterium, remains a scientific challenge. Domestic ruminants are considered the main reservoir, shedding C. burnetii essentially through parturition products during abortion or birth. Sheep are particularly frequently associated with human outbreaks, but there are insufficient field data to fully understand disease dynamics and to instigate efficient control measures. A longitudinal follow-up study of a naturally infected sheep flock was performed (i) to investigate relationships between seropositivity and bacterial shedding in the vaginal mucus, (ii) to describe the kinetics of antibodies, including responses to vaccination, (iii) to monitor maternal antibodies in ewe lambs, and (iv) to compare serological results for milk and serum samples. For 8 months, we collected blood samples every 3 weeks from 11 aborting and 26 nonaborting dairy ewes, 20 nonaborting suckler ewes, and 9 ewe lambs. Individual milk samples were also obtained from lactating females. All serum and milk samples were tested by enzyme-linked immunosorbent assay (ELISA), whereas vaginal swabs were tested by quantitative PCR. We found that some dairy females did not seroconvert despite shedding C. burnetii in their vaginal mucus. Overall, antibody levels in adult females were found to remain stable over time, with exceptions during the mating and lambing periods. Maternal antibodies decreased during the first month after birth. Interestingly, antibody levels in milk were correlated with those in serum. This study provides valuable field data that will help improve Q fever surveillance and within-flock management measures.IMPORTANCE Field data are necessary to improve the surveillance, diagnosis, and sanitary management of Q fever in livestock. Here, we provide extensive serological data obtained from serum and milk samples from infected and vaccinated ewes belonging to a naturally infected flock of sheep. We show that antibody levels are stable over time and seropositivity and vaginal shedding are not clearly correlated, whereas antibody levels in milk are strongly correlated with those in serum. Accordingly, we find that antibody levels in bulk tank milk are consistent with the variations observed in the serum of dairy females over time. We report the existence of maternal antibody transmission to ewe lambs and we show that the presence of maternal antibodies at birth does not prevent the development of a serological response to vaccination at the age of 4 months. Finally, we report that adult ewes generally seroconvert after vaccination, including during pregnancy.

Quantification of resistant alleles in the \u03b2-tubulin gene of field strains of gastrointestinal nematodes and their relation with the faecal egg count reduction test

BackgroundBenzimidazole (BZ) resistance in gastrointestinal nematodes is associated with a single nucleotide polymorphism (SNP) at codons 167, 198 and 200 in the isotype 1 of beta-tubulin gene although in some species these SNPs have also been associated with resistance to macrocyclic lactones. In the present study we compared the levels of resistance in Teladorsagia circumcincta and Trichostrongylus colubriformis by means of the faecal egg reduction test (FECRT) and the percentage of resistant alleles obtained after pyrosequencing. The study was conducted in 10 naturally infected sheep flocks. Each flock was divided into three groups: i) group treated with albendazole (ABZ); ii) group treated with ivermectin (IVM); iii) untreated group. The number of eggs excreted per gram of faeces was estimated at day 0 and 14 post-treatment.ResultsResistance to ABZ was observed in 12.5% (1/8) of the flocks and to IVM in 44.4% (4/9) of them. One flock was resistant to both drugs according to FECRT. Coprocultures were performed at the same dates to collect L3 for DNA extraction from pooled larvae and to determine the resistant allele frequencies by pyrosequencing analysis. In T. circumcincta, SNPs were not found at any of the three codons before treatment; after the administration of ABZ, SNPs were present only in two different flocks, one of them with a frequency of 23.8% at SNP 167, and the other 13.2% % at SNP 198. In relation to T. colubriformis, we found the SNP200 before treatment in 33.3% (3/9) of the flocks with values between 48.5 and 87.8%. After treatment with ABZ and IVM, the prevalence of this SNP increased to 75 and 100% of the flocks, with a mean frequency of 95.1% and 82.6%, respectively.ConclusionThe frequencies observed for SNP200 in T. colubriformis indicate that the presence of resistance is more common than revealed by the FECRT.

Evidence of co-infection with Mycobacterium bovis and tick-borne pathogens in a naturally infected sheep flock

Ticks are responsible for the transmission of pathogens of veterinary importance, including those affecting sheep. The current study was designed to investigate co-infections with tick-borne and other pathogens in a naturally infected sheep flock with poor health condition using serology and PCR. Infection with Anaplasma ovis was detected by serology and PCR in 56% of the animals. The presence of Rickettsia spp. of the Spotted Fever Group (SFG) was detected by PCR and sequence analysis in 31% of the animals. All the animals were negative for Anaplasma phagocytophilum either by serology or PCR. Twelve sheep were randomly selected for anatomopathological studies. Five of these animals presented lesions consistent with Mycobacterium tuberculosis complex (MTBC) infection and spoligotyping confirmed infection with Mycobacterium bovis spoligotype SB0339. Co-infection with tick-borne pathogens and MTBC could contribute to the poor health condition observed in these animals but other uncontrolled factors may also be responsible. The differential expression of immune response genes supported previous findings in ruminants and suggested that infection with tick-borne pathogens and M. bovis may results in unique gene expression patterns in sheep. The results underline the need for further research into the possible role of sheep in the epidemiology of animal tuberculosis.

Failure of ivermectin treatment in Haemonchus contortus infected-Swedish sheep flocks

Control of gastrointestinal nematodes of veterinary importance in Swedish sheep flocks is primarily based on recurring strategic anthelmintic treatments after detection of strongyle eggs in faeces samples. This study reports reduced efficacy of ivermectin (IVM) against Haemonchus contortus in naturally infected Swedish sheep flocks. Faecal egg count reduction tests (FECRT) and examinations of H. contortus-specific DNA with qPCR on larval cultures were applied to samples from 11 sheep flocks (A–K) in south-eastern Sweden between 2013 and 2014. Four of these flocks (D, E, J and K) had been in direct contact with flock H, where IVM treatment failure was first observed in October 2013, some years after the introduction of imported dairy sheep. In flock H, the resistance status to IVM was also confirmed by a larval developmental test. IVM concentrations 15–20 times higher than for susceptible strains of H. contortus were required to kill the larvae. In addition, faeces samples were obtained from 37 other Swedish sheep farms where the treatment response to IVM was screened initially in six animals using FEC and qPCR 7–10days after administration of IVM. Six farms where the majority was identified with this pre-screening test (B, C, F, G, I and K), were also investigated in more detail with FECRT as described above after the animals had been allocated to groups and treated orally or injected with a minimum of 0.2mg IVM, 0.2mg doramectin (farm F) or 0.2mg moxidectin per kg body weight (farm A and B). Four flocks (farm A, D, G and I) were also treated with 4.8mg albendazole and/or 7.5mg levamisole per kg body weight. Pre-treatment faeces samples were collected from 15 animals on the same day as deworming. Post-treatment samples were collected 7–10days later, whenever possible from 10 animals per group with the highest pre-treatment egg counts. Based on FECRT results, IVM efficacy to H. contortus was reduced on six farms (C, D, E, G, H and I) out of 11 farms studied with FECRT. This is the first report of IVM treatment failure in H. contortus-infected sheep in Sweden.

Serological diagnosis of FMD in sheep in Basra by ELISA test

This study was performed to detect the antibodies against the virus-infection- associated antigen (VIAA) in previously diseased and healthy sheep in Basra. The test is valuable in epizootiological surveys because only infected animals with foot and mouth disease virus will give positive reaction without detection of the virus serotypes. 241 sheep sera were collected from 13 suspicious infected sheep flocks with FMD from two major areas in Basra (Abulkhaseeb and Alzubair). All these samples were examined by ELISA test to VIA antigen. It was found -by ELISA- that 71.9% of the total tested sheep sera build specific VIA antibodies against FMD virus, and that 91.7% of the clinically infected sheep gave positive result and that 66.8% of the clinically non-infected sheep were negative. The higher rate of seropositivity in both Abuelkhaseeb and AL-Zubair areas was in the age between 3.5 – 4.5 year (80%) and (81.8%) respectively. The high prevalence of seropositivity to VIA could be due to sub clinical infection or to carrier state and the disease in sheep mild and go un-noticed but important because of transmission to cattle.

Comparative impact of conventional and strategic worm management schemes in sheep flocks of arid Rajasthan

A study on comparative impact (in terms of worm profile and flock performance) of two schemes of worm management in naturally infected sheep flocks was made in arid Rajasthan. During the period from May 2004 to March 2012, sheep(8415) were monitored for gastrointestinal strongyles by examining 24,310 faecal samples as well as for production performance of flock. The monthly incidence and intensity of strongyle nematodes remained almost similar among flocks given either strategic (one drench/annum) or conventional (3 drenches/annum) anthelmintic treatment. The epidemiological profile exhibited higher magnitude of infection only during monsoon (June-October). The data on flock performance exhibited that reduction in anthelmintic frequency in strategic scheme as against conventional scheme had no adverse effect on flock performance and yields better financial return to farmers. The result reflected the value and success of single drench schedule (strategic scheme) for the effective management of predominant gastrointestinal nematodes in field flocks of arid Rajasthan which is based on systematically gathered epidemiological information.

The diagnosis of fasciolosis in feces of sheep by means of a PCR and its application in the detection of anthelmintic resistance in sheep flocks naturally infected

The aim of this study was to develop a PCR for the diagnosis of Fasciola hepatica infection in feces of sheep based on the ribosomal internal transcribed spacer. Detection of infection was possible from the second week post-infection in experimentally infected sheep by amplification of a 292bp fragment. This PCR was employed for the detection of anthelmintic resistance (AR) in naturally infected sheep flocks, and results were compared with techniques such as the fecal egg count reduction test (FECRT) and the copro-antigen reduction test (CRT). The FECRT was carried out in two flocks, Santillan de la Vega (SV) and Corullón (CR), with sheep treated with albendazole (ABZ), clorsulon (CL), or triclabendazole (TCBZ). Feces were collected from individuals on days 0, 7, 15, and 30 post-treatment (pt). The FECRT showed adult F. hepatica to be resistant to ABZ and CL in both flocks. All parasite stages in the SV flock were susceptible to TCBZ, while in the CR flock, adult flukes showed resistance and immature forms were susceptible to the treatment. To compare FECRT and the PCR results, we calculated the percent of positive sheep on day 1 pt. In both flocks, the percent positive sheep was consistently higher by PCR than by sedimentation, confirming that the PCR is a more sensitive method of diagnosing infection and therefore to detect the resistance in infected animals. The CRT was carried out in the SV flock using a sandwich ELISA kit. The percent of sheep found positive by PCR was higher than with ELISA. Comparison of FECRT, CRT, and PCR for the detection of AR showed PCR to be the most sensitive.

Evaluation of conventional and strategic worm management schemes in sheep flocks of semi-arid Rajasthan

A comparison of parasitological status and economic benefit derived from 2 schemes of worm management in naturally infected sheep flocks was made in semi-arid Rajasthan. During the period from June 2004 to March 2011, sheep (8061) were monitored for productive performance and evaluated for gastrointestinal strongyles by examining 25172 faecal samples. The monthly incidence and intensity of strongyle nematodes remained almost similar among flocks given either strategic (1 drench/annum) or conventional (3 drenches/annum) anthelmintic treatment. The epidemiological profile exhibited higher magnitude of infection only during monsoon (July-October). The comparative economic evaluation showed that reduction in anthelmintic frequency in strategic scheme as against conventional scheme had no adverse effect on flock performance and yields better financial return to farmers. The result reflected the value and success of single drench schedule (strategic scheme) for the effective management of predominant gastrointestinal nematodes in field flocks of semi-arid Rajasthan which is based on relevant epidemiological information.

Evaluation of the efficacy of oxytetracycline treatment followed by vaccination against Q fever in a highly infected sheep flock

The aim of this research was to evaluate the efficacy of oxytetracycline treatment following an outbreak of Q fever in a sheep flock when gestation is too advanced for vaccination to be used. In such cases, immediate application of antibiotics is needed and vaccination postponed until the next breeding season. Seventy-five per cent of ewes from a dairy sheep flock affected by Q fever were treated with oxytetracycline at approximately days 100 and 120 of gestation, with the remaining 25% of the animals kept as untreated controls. Vaginal swabs, faeces and milk samples from 81 ewes (57 treated, 24 untreated) were analysed by PCR within 30 days of lambing and revealed a high percentage of Coxiella burnetii shedders. No significant differences were found between groups in either the percentage of shedders or in the mean amount of bacteria shed. In the following season 75% of the ewes and 50% of the replacement ewe lambs were vaccinated with a phase I vaccine prior to artificial insemination. Both vaccinated and control groups were homogeneously composed of ewes treated and untreated with antibiotics in the previous season. The number of shedders and the bacterial excretion load decreased significantly compared to the previous season but no statistically significant differences were found between vaccinated and control groups. In addition, no significant effect derived from the application of oxytetracycline in the previous season was observed. Vaccination was repeated for the following two seasons, and the percentage of animal shedders was reduced to minimal levels highlighting the importance of vaccination over the longer term.

Efficacy of nitroxynil against Fasciola hepatica resistant to triclabendazole in a naturally infected sheep flock

The aim of this study was to compare the efficacy of triclabendazole (TCBZ) and nitroxynil against a TCBZ-resistant Fasciola hepatica strain in a naturally infected sheep flock. The efficacies were measured by the faecal egg count reduction test. The level of F. hepatica antigens was tested in faeces; and haematological indices such as total proteins (TP), albumin, hepatic enzymes and total IgG were also studied. The results confirmed the resistance of F. hepatica against TCBZ in the flock with an efficacy during the first month post-treatment between 59.4% and 73.8%. In the nitroxynil group, the efficacy during the same period ranged between 81.3% and 86%, likely because the efficacy of this drug against 7- to 9-week-old immature stages is only 50-90%. Anemia was showed in all groups and white blood cells were always higher than the reference range. The values of TP and albumin were within normal range in most of the sheep, and an increase in hepatic enzymes confirmed the liver damage. Regarding total IgG, some negative correlations were found with egg excretion, and in relation to the level of antigens in faeces, these ones decreased immediately after treatment. We conclude that nitroxynil could be an alternative in case of TCBZ resistance.

Characterization of Anaplasma phagocytophilum and A. ovis infection in a naturally infected sheep flock with poor health condition

Anaplasma species are transmitted by ticks and cause diseases in humans and animals. These pathogens infect sheep, an economically important domestic animal worldwide. The current study was designed to characterize in 200 animals the infection with Anaplasma phagocytophilum and Anaplasma ovis and the genetic diversity of A. ovis strains collected from a naturally infected sheep flock with poor health condition. Sheep had 98% seroprevalence to Anaplasma spp. antibodies. PCR results confirmed the presence of A. phagocytophilum and A. ovis DNA in 11.5% and 37% of the sheep, respectively. Concurrent infections were detected in 6.5% of the sheep. Seventy-one adult ticks were collected from 45 sheep with infestations ranging from one to 15 ticks per animal. The analysis of A. ovis msp4 sequences demonstrated a previously unreported polymorphism for this pathogen with 17 different haplotypes in infected sheep. These results demonstrated that, although A. ovis msp4 haplotypes may be less variable when compared with Anaplasma marginale and A. phagocytophilum strains on a global scale, genetic polymorphisms occur in this locus in strains obtained from an infected sheep flock with poor health condition.