Infected Ewes Research Articles

Role of carriers in the transmission of pneumonia in bighorn sheep (Ovis canadensis)

ABSTRACTIn the absence of livestock contact, recurring lamb mortality in bighorn sheep (Ovis canadensis) populations previously exposed to pneumonia indicates the likely presence of carriers of pneumonia-causing pathogens, and possibly inadequate maternally derived immunity. To investigate this problem we commingled naïve, pregnant ewes (n=3) with previously exposed rams (n=2). Post-commingling, all ewes and lambs born to them acquired pneumonia-causing pathogens (leukotoxin-producing Pasteurellaceae and Mycoplasma ovipneumoniae), with subsequent lamb mortality between 4-9 weeks of age. Infected ewes became carriers for two subsequent years and lambs born to them succumbed to pneumonia. In another experiment, we attempted to suppress the carriage of leukotoxin-producing Pasteurellaceae by administering an antibiotic to carrier ewes, and evaluated lamb survival. Lambs born to both treatment and control ewes (n=4 each) acquired pneumonia and died. Antibody titers against leukotoxin-producing Pasteurellaceae in all eight ewes were ‘protective’ (>1:800 and no apparent respiratory disease); however their lambs were either born with comparatively low titers, or with high (but non-protective) titers that declined rapidly within 2-8 weeks of age, rendering them susceptible to fatal disease. Thus, exposure to pneumonia-causing pathogens from carrier ewes, and inadequate titers of maternally derived protective antibodies, are likely to render bighorn lambs susceptible to fatal pneumonia.

Erratum to: Postpartum pathology in Yankasa ewes experimentally infected with Trypanosoma evansi during pregnancy

The study was designed to determine the pathological changes in postpartum Yankasa ewes experimentally infected with Trypanosoma evansi (T. evansi) during pregnancy. Thirteen pregnant Yankasa ewes were divided into two groups comprising six ewes in group A and seven ewes in group B. Ewes in group A served as the uninfected control while ewes in group B were infected with approximately 1.0 × 106 of T. evansi per ewe through the jugular vein at the second trimester of pregnancy. They were closely monitored for trypanosomosis from the time of infection up till parturition. One ewe from each group was humanely sacrificed 10 days postpartum and examined for pathological changes. At postmortem, no gross lesion was seen in the infected and control ewes and their placenta. Histologically, there were no changes on the placenta, reproductive tract (ovary, oviduct, uterus, cervix), and viscera organs (liver, lungs, heart, kidney, and spleen) of both infected and control ewes. However, the infected ewe had histopathological changes in the hypothalamus characterized by neuronal degeneration and microglial infiltration, while in the pituitary gland, there was mononuclear cell infiltration. The thyroid gland was infiltrated by inflammatory macrophages and lost its glandular secretions. All these histopathological changes were absent in the uninfected ewe, suggesting that T. evansi is capable of disrupting the endocrine function of reproduction in Yankasa ewes.

Bayesian estimation of sensitivity and specificity of a commercial serum/milk ELISA against the Mycobacterium avium subsp. Paratuberculosis (MAP) antibody response for each lactation stage in Greek dairy sheep

A total of 854 paired milk and blood samples were collected from ewes of a Greek flock and used to estimate the sensitivity and specificity of a commercial ELISA for detection of Mycobacterium avium subsp. paratuberculosis (MAP) specific antibodies in each stage of lactation. We implemented Bayesian mixture models to derive the distributions of the test response for the healthy and the infected ewes. In the colostrum period, early, mid and late lactation stage the median values of the area under the curves (AUC) were 0.61 (95% credible interval: 0.50; 0.84), 0.61 (0.51;0.84), 0.65 (0.51;0.91), 0.65(0.51;0.89) for the serum ELISA and and 0.60 (0.50; 0.84), 0.61 (0.50; 0.84), 0.67(0.51; 0.91), 0.66(0.50; 0.90) for the milk ELISA, respectively. Both serum and milk ELISA had low to average overall discriminatory ability as measured by the area under the curves and comparable sensitivities and specificities at the recommended cutoffs.

Effects of experimental Trypanosoma evansi infection on pregnancy in Yankasa ewes

Twenty pregnant Yankasa ewes were assigned to three groups to determine the effect of Trypanosoma evansi infection on pregnancy. Groups A and B comprising seven ewes each were infected with approximately 1.0 × 106 cells of T evansi per ewe through venepuncture at the second and third trimesters of pregnancy, respectively. Group C comprising six ewes served as uninfected control. There was slight pyrexia in the infected groups (groups A and B) but was absent in group C. The mean body weight, glucose concentration, and packed cell volume of ewes in group A were not significantly different from those in group C throughout the study. There was also no significant difference in mean glucose concentration between groups B and C. However, in group B, mean body weight was significantly (P < 0.05) lower compared to group C at week 2 and from week 4 post infection (pi) till the end of the study; the packed cell volume also significantly (P < 0.05) decreased but at weeks 4 and 6 pi. The mean plasma protein of ewes in group A was significantly (P < 0.05) increased compared to those of group C at weeks 7, 11 pi and thereafter till the end of the study. On the contrary, the plasma protein of ewes in group B decreased significantly (P < 0.05) compared to those in group C at weeks 2 and 6 pi. There were no reproductive losses throughout the study. This was characterized by insignificant differences in the gestation length between ewes in the infected groups (groups A and B) compared with those in group C. However, there were significant (P < 0.05) decreases in lamb birth weights of ewes in group B compared with ewes in groups A and C. Mice inoculation with blood from infected ewes postpartum was parasitemic 18 to 25 days pi, for ewes in group B, whereas none of the mice in groups A and C were parasitemic. Lambs born from the infected groups (groups A and B) were also aparasitemic for 40 days postpartum. It was therefore concluded that the T evansi isolate used caused mild trypanosomosis when infected at third trimester, whereas ewes infected at second trimester were resistant.

Experimental infection by Trypanosoma evansi in sheep: Occurrence of transplacental transmission and mice infection by parasite present in the colostrum and milk of infected ewes

The aims of this study were to evaluate vertical transmission of Trypanosoma evansi in sheep experimentally infected, in addition to the mammary transmission by colostrum or milk of these infected sheep to mice. Three pregnant sheep were used: one uninfected, four months pregnant (Sheep A); and two (Sheep B and C) infected intravenously by T. evansi trypomastigotes (4.6×106 per animal) on the third (Sheep C) and fourth (Sheep B) month of pregnancy. Both infected sheep developed low and oscillating parasitemia measured by blood smears. Hemogram was performed at seven day intervals, showing anemia, leukocytosis, and lymphocytosis on sheep B and C. Three sheep had twins, where sheep A delivered healthy lambs and both infected sheep had delivered at least one stillborn. Additionally, lambs from sheep B and C died 24 and 72h post-partum, respectively. Before colostrum intake, four lambs from infected sheep were positives for T. evansi according to blood smear evaluation, serology (CATT/T. evansi), and PCR. Sheep colostrum and milk samples collected from the first four days post-partum were positives for T. evansi on PCR, and these samples were able to infect seven mice (out of 10) orally (n=4/5) and intraperitoneally (n=3/5). Therefore, we conclude that the vertical transmission of T. evansi occurs in pregnant sheep, in addition to a strong possibility of the transmission by colostrum and milk.

Study on the use of toltrazuril to eliminate Neospora caninum in congenitally infected lambs born from experimentally infected ewes

To determine if toltrazuril was effective in eliminating Neospora caninum infection from congenitally infected lambs. Twenty-eight ewes were allocated to 3 groups where animals in Groups A and B were inoculated with 1×107 N. caninum tachyzoites on Day 120 of gestation and Group C was maintained as a negative control group. Lambs born from ewes in Group A were treated with toltrazuril (20mg/kg) on Days 0, 7, 14 and 21 after birth. Lambs in Groups B and C were untreated. All lambs in Groups A and B were seropositive at 12 weeks of age. At 12 weeks of age, no differences between lambs in Group A and Group B were observed in serological results (ELISA and western blot), presence of N. caninum-related brain histopathological lesions or the number of organisms detected by qPCR. Group C remained negative for serology, detection of N. caninum DNA as well as histopathology throughout the study. Results indicate that N. caninum congenitally-infected lambs had a continuing infection with N. caninum despite being treated with toltrazuril.

Strategic control of gastrointestinal nematodes in grazing sheep with a long-acting moxidectin formulation

A field study was undertaken on three Swiss sheep farms (A, B, C) to evaluate the efficacy of a long-acting moxidectin formulation (Cydectin® 2% LA) against gastrointestinal nematodes (GIN). Naturally infected ewes (all three farms) and their winter-borne lambs (farms A and B) were allocated to two groups (MOX, CON). At day 0 ewes of the MOX-groups were treated with 1mg moxidectin s.c. CON- and MOX-groups were grazed on separate pastures and were sampled for faeces and blood at 28-day intervals. Larval cultures demonstrated that Haemonchus contortus was the dominant GIN-species in ewes throughout the season. Over the entire observation period faecal egg count (FEC) of the MOX-ewes in farms A, B, C was 56%, 84% and 87% less than the CON-ewes (p<0.05). FEC of lambs grazing with MOX-ewes was reduced in farms A and B by 56% and 61%, respectively (p<0.05), compared with the respective CON-groups. None of these lambs received anthelmintic treatment during the experiment. Therefore, the differences were due to an indirect effect mediated by the lower pasture contamination with GIN-larvae. These were reduced by 73%, 81% and 74% in farms A-C respectively compared to the CON-groups (p<0.05). In farm B, where lambs remained with their mothers during the entire grazing season, these differences were also reflected by a higher daily weight gain (p<0.05) and reduced pepsinogen levels in lambs of treated ewes. This strategy offers an interesting potential for expanding refugia by propagation of GIN in untreated lambs.

Effect of Moxidectin Treatment at Peripartum on Gastrointestinal Parasite Infections in Ewes Raised under Tropical Andes High Altitude Conditions.

This study tested the impact of moxidectin at peripartum on nematode fecal egg count (FEC) and clinical parameters on ewes in the high altitude tropical Andes of Colombia. FEC and clinical evaluations were performed on 9 occasions in 43 naturally infected ewes before and during gestation and after lambing. Moxidectin (Mox, 200 µg kg−1) was applied at late pregnancy (T 1, n = 15) or 48 hours after parturition (T 2, n = 14). 14 untreated ewes served as controls (C). Suckling lambs (n = 58) remained untreated and underwent four clinical and parasitological evaluations until 8 weeks after birth. Mox efficacy equaled 99.3% (T 1) and 96.9% (T 2). Highest mean FEC value reflecting periparturient nematode egg rise (PPER) was recorded in C ewes at 4–6 weeks after lambing. Significant FEC reductions were found in T 1 (94.8%) and T 2 (96.7%) ewes (p < 0.05). All lambs showed a significant and ewes-group independent increase in FEC before weaning (p < 0.05). Clinical parameters (anemia and diarrhea) showed time- and treatment-related differences (p < 0.05). Monitoring of FEC and clinical parameters linked to gastrointestinal parasite infections allowed demonstrating that postpartum or preweaning are two critical periods to nematode infection for sheep raised under tropical Andes high altitude conditions. Use of Mox as anthelmintic treatment prevented PPER.

Molecular Identification of Limited Cases of Rift Valley Fever Virus Infection and Associated Oxidative Stress Status as Sequential Steps in Ewes in Egypt

Molecular Identification of Limited Cases of Rift Valley Fever Virus Infection and Associated Oxidative Stress Status as Sequential Steps in Ewes in Egypt Rift valley fever is caused by a virus of the family Bunyaviridae and the genus Phlebovirus, affects domestic ruminant and human, causing severe economic losses. In the present study, venous blood samples were obtained from 30 randomly selected clinically healthy ewes (control group) and another 30 ewes suspected to be infected with rift valley fever virus in Egypt. Diseased ewes showed fever without abortion and some ewes exhibit respiratory and/or digestive disorders. Reverse transcription-Polymerase chain reaction (RT-PCR) was used for molecular identification of rift valley fever virus. Viral RNA was detected in 9 samples by RT-PCR. Oxidative stress status was evaluated in rift valley fever infected ewes. In the diseased ewes, there was a significant (p<0.05) decrease in the total antioxidant capacity and activity of reduced glutathione, catalase and superoxide dismutase as well as level of zinc and iron. However, there was a significant (p<0.05) increase in the level of nitric oxide, hydrogen peroxide, malondialdehyde, interleukin-6 and tumor necrosis factor-α. Moreover, the oxidative stress index was significantly (p<0.05) increased in ewes with rift valley fever compared with control group. In conclusion, rift valley fever virus infection is confirmed in limited cases of ewes in Egypt. RT-PCR is rapid and specific method for laboratory diagnosis of the disease. Furthermore, oxidative stress, with alteration of antioxidant enzymes activity, antioxidant trace element levels, and pro-inflammatory cytokines, is a feature of rift valley fever virus infection in diseased ewes.

Reproductive performance in experimentally BVDV infected ewes and seroconversion rates in sheep co-mingled with BVDV PI calves

Bovine viral diarrhoea virus (BVDV) is an economically important disease of cattle, causing severe reproductive losses and immunosuppressive effects in cattle populations worldwide. Before a national BVDV control programme can be developed in Australia, it is important to explore the possibility of sources of transmission from and through alternative susceptible populations, such as sheep.Transmission of BVDV to species other than cattle has been shown to occur following both experimental and natural infection of other ruminants. The aims of this study were to investigate the impact of an experimental infection with a local Australian strain of BVDV (Type 1c) on the reproductive performance of pregnant ewes and the potential for natural transmission of BVDV from persistently infected (PI) cattle to naive sheep.Twenty-three BVDV naïve, pregnant ewes were experimentally infected with BVDV by subcutaneous inoculation with 2mL freeze-thawed PI cow serum. Severe reproductive losses including low lambing rates and a high number of young lamb deaths were seen in these ewes. One PI lamb was also produced in this trial, but died at 15 days of age.Nine BVDV naïve sheep wethers were co-mingled with three BVDV PI calves in a 1500sqm paddock for four weeks. Transmission of infection, as indicated by seroconversion, occurred in four of nine wethers during a four-week period of co-mingling.The trials suggest that the potential for infection with BVDV derived from cattle for sheep exists and needs to be taken into account when controlling BVDV infection in cattle.

Insights into potential pathogenesis mechanisms associated with Campylobacter jejuni-induced abortion in ewes.

BackgroundCampylobacter jejuni is commonly found in the gastrointestinal tract of many food-animals including sheep without causing visible clinical symptoms of disease. However, C. jejuni has been implicated in ovine abortion cases worldwide. Specifically, in the USA, the C. jejuni sheep abortion (SA) clone has been increasingly associated with sheep abortion. In vivo studies in sheep (the natural host) are needed to better characterize the virulence potential and pathogenesis of this clone.ResultsPregnant ewes intravenously (IV) or orally inoculated with ovine or bovine abortion-associated C. jejuni SA clones exhibited partial or complete uterine prolapse with retained placenta, and abortion or stillbirth, whereas delivery of healthy lambs occurred in pregnant ewes inoculated with C. jejuni 81–176 or in the uninfected group. In sheep inoculated with the SA clone, histopathological lesions including suppurative necrotizing placentitis and/or endometritis coincided with: 1) increased apoptotic death of trophoblasts, 2) increased expression of the host genes (e.g. genes encoding interleukin IL-6 and IL-15) related to cellular necrosis and pro-inflammatory responses in uterus, and 3) decreased expression of the genes encoding GATA binding protein 6, chordin, and insulin-like 3 (INSL3) that account for embryonic development in uterus. Immunohistochemistry revealed localization of bacterial antigens in trophoblasts lining the chorioallantoic membrane of ewes inoculated with the C. jejuni SA clone.ConclusionsThe results showed that C. jejuni SA clones are capable of causing abortion or stillbirth in experimentally infected sheep. Furthermore, down- or up-regulation of specific genes in the uterus of infected pregnant ewes might implicate host genes in facilitating the disease progression. Since the C. jejuni SA strains share genotypic similarities with clones that have been isolated from human clinical cases of gastroenteritis, these strains might represent a potential public health risk.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-014-0274-8) contains supplementary material, which is available to authorized users.

Determination of milk production losses in Valle del Belice sheep following experimental infection of Mycoplasma agalactiae

Economic losses due to contagious agalactia (CA) in small ruminant herds are mainly associated with significant reductions in or complete loss of dairy production, mortality, abortions, ill thrift, early culling and costs of control. With the aim of estimating milk production losses caused by CA, 46 primiparous lactating Valle del Belice ewes were monitored after experimental infection. Sixty days after lambing, two ewes were each experimentally infected with a single dose of 108CFU/ml of a live Mycoplasma agalactiae strain in both teats by intracanalicular route. Three days after inoculation, the infection was spread manually by the milkers dipping their hands in the pooled milk from the experimentally infected ewes just before milking each of the uninfected sheep. The milk yield was recorded daily (morning and evening) for 12 weeks: 5 weeks before and 7 weeks after infection. Daily milk data, collected from each ewe, were used to design individual lactation curves in order to estimate the impact of CA infection. Individual milk samples were screened for the presence of M. agalactiae as well other pathogens which cause mastitis in small ruminants comprising Staphylococcus aureus, coagulase negative-staphylococci (CNS), Corynebacterium spp. and Streptococcus spp. No pathogens were detected in the milk of 10 (22%) of the 46 ewes kept with the experimentally infected sheep. There was a reduction of 17% in milk output of 19 (41%) ewes from which M. agalactiae was isolated; the 17 (37%) remaining ewes had a similar drop in milk production but recovered quickly within 2–3 weeks, so the final losses were estimated to be 3%. The infected milk showed a significantly higher somatic cell count when mycoplasma excretion in milk was >103 CFU/ml. Percentages of milk protein and casein were higher in milk excreting M. agalactiae due to concentration, in contrast the percentage of lactose in the milk was significantly lower. No significant effect of M. agalactiae was found on the percentage of milk fat.In conclusion, the loss of milk following CA infection is variable and probably related to the degree of exposure and capacity of the individual ewe to resist the pathogen.

Effect of selenium yeast supplementation on naturally acquired parasitic infection in ewes.

Gastrointestinal parasites cause substantial economic losses in pasture-based sheep production systems. Supranutritional organic selenium (Se) supplementation may be beneficial because it improves immune responses to pathogens. To evaluate the effect of Se-yeast supplementation on gastrointestinal parasite load, 30 ewes per treatment group were drenched weekly with no Se, 4.9mg Se/week as Se yeast (maximum FDA-allowed concentration), or supranutritional concentrations of Se yeast (14.7 and 24.5mg Se/week) starting early fall for 85weeks. Fecal samples were collected at weeks 63, 66, 78, and 84 and counted for total trichostrongyle-type eggs and Haemonchus contortus eggs (in samples with ≥200 trichostrongyle eggs/g feces). During breeding season (fall), ewes were kept on pasture; ewes receiving 24.5mg Se/week had lower fecal trichostrongyle egg counts (93 ± 40 eggs/g feces) compared with ewes receiving no Se (537 ± 257 eggs/g feces; P = 0.007) or ewes receiving 4.9mg Se/week as Se yeast (398 ± 208 eggs/g feces; P = 0.03). In winter, fecal trichostrongyle egg counts decreased, and group differences were not apparent. During lambing season (spring), ewes were kept in the barn and fecal trichostrongyle egg counts increased, although no group differences were observed. However, none of the ewes receiving supranutritional Se yeast, and with trichostrongyle egg counts ≥200 eggs/g of feces, but four of the ewes receiving lower Se dosages had H. contortus egg counts ≥1,000 eggs/g feces (P = 0.04). Our results suggest that supranutritional Se-yeast supplementation may enhance resistance to naturally occurring H. contortus gastrointestinal parasitism in sheep.

Correlation between FMDV and Antibodies in Milk and Blood of Infected Lactating Ewes

Correlation between FMDV and Antibodies in Milk and Blood of Infected Lactating Ewes

PREVALENCE OF LEPTOSPIROSIS IN EGYPTIAN SHEEP FLOCK

A sheep flock contains 600 head of Al-Barky ewes suffered from: Icterus, bloody urine, death two days post symptoms appearance and abortion in 6 pregnant ewes. Thesymptoms appeared on 46 case and 6 ewes aborted and mortality rate was44 case dead. The results of examined samples showed that the isolation of leptospira from 5 out of 52 (9.62 %) animals samples (blood, urine and necropsy kidney tissue samples), the isolates were 2 from blood samples (6.7 %), 2 from kidney samples (6.7 %) and 1 from urine samples (10 %). The obtained leptospira isolates from infected ewes were examined by PCR for identification of leptospires, using universal primers set (lig1 / lig2,) that amplify the genomic DNA of all pathogenic Leptospiraserovar only, the most predominant seropositivity using MAT was detected against L.int.icterohaemorrhagiae (57.69%), followed by L.int.grippotyphosa (28.85%) and L.int.pomona (13.46%). The highest titer of seropositivity was detected against serovarL.int.icterohaemorrhagiae (1:1600) while L.int.grippotyphosa and L.int.pomona reached up to (1:400).

Placental thrombosis in acute phase abortions during experimental Toxoplasma gondii infection in sheep

After oral administration of ewes during mid gestation with 2000 freshly prepared sporulated oocysts of T. gondii isolate M4, abortions occurred between days 7 and 11 in 91.6% of pregnant and infected ewes. Afterwards, a further infection was carried out at late gestation in another group of sheep with 500 sporulated oocysts. Abortions happened again between days 9 and 11 post infection (pi) in 58.3% of the infected ewes. Classically, abortions in natural and experimental ovine toxoplasmosis usually occur one month after infection. Few experimental studies have reported the so-called acute phase abortions as early as 7 to 14 days after oral inoculation of oocysts, and pyrexia was proposed to be responsible for abortion, although the underline mechanism was not elucidated. In the present study, all placentas analysed from ewes suffering acute phase abortions showed infarcts and thrombosis in the caruncullar villi of the placentomes and ischemic lesions (periventricular leukomalacia) in the brain of some foetuses. The parasite was identified by PCR in samples from some placentomes of only one sheep, and no antigen was detected by immunohistochemical labelling. These findings suggest that the vascular lesions found in the placenta, and the consequent hypoxic damage to the foetus, could be associated to the occurrence of acute phase abortions. Although the pathogenesis of these lesions remains to be determined, the infectious dose or virulence of the isolate may play a role in their development.

Correction: Evidence in Sheep for Pre-Natal Transmission of Scrapie to Lambs from Infected Mothers

Natural scrapie transmission from infected ewes to their lambs is thought to occur by the oral route around the time of birth. However the hypothesis that scrapie transmission can also occur before birth (in utero) is not currently favoured by most researchers. As scrapie is an opportunistic infection with multiple infection routes likely to be functional in sheep, definitive evidence for or against transmission from ewe to her developing fetus has been difficult to achieve. In addition the very early literature on maternal transmission of scrapie in sheep was compromised by lack of knowledge of the role of the PRNP (prion protein) gene in control of susceptibility to scrapie. In this study we experimentally infected pregnant ewes of known PRNP genotype with a distinctive scrapie strain (SSBP/1) and looked for evidence of transmission of SSBP/1 to the offspring. The sheep were from the NPU Cheviot flock, which has endemic natural scrapie from which SSBP/1 can be differentiated on the basis of histology, genetics of disease incidence and strain typing bioassay in mice. We used embryo transfer techniques to allow sheep fetuses of scrapie-susceptible PRNP genotypes to develop in a range of scrapie-resistant and susceptible recipient mothers and challenged the recipients with SSBP/1. Scrapie clinical disease, caused by both natural scrapie and SSBP/1, occurred in the progeny but evidence (including mouse strain typing) of SSBP/1 infection was found only in lambs born to fully susceptible recipient mothers. Progeny were not protected from transmission of natural scrapie or SSBP/1 by washing of embryos to International Embryo Transfer Society standards or by caesarean derivation and complete separation from their birth mothers. Our results strongly suggest that pre-natal (in utero) transmission of scrapie may have occurred in these sheep. Citation: Foster JD, Goldmann W, Hunter N (2013) Evidence in Sheep for Pre-Natal Transmission of Scrapie to Lambs from Infected Mothers. PLoS ONE 8(11): e79433. doi:10.1371/journal.pone.0079433 Editor: Ilia V. Baskakov, University of Maryland School of Medicine, United States of America Received September 11, 2013; Accepted September 19, 2013; Published November 18, 2013 Copyright: 2013 Foster et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The project was funded by Defra (UK Department for the Environment, Food and Rural Affairs) Grant number SE1823 (www.gov.co.uk/defra) with core support funding to the Institute for Animal Health from BBSRC (UK Biotechnology and Biological Sciences Research Council). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: nora.hunter@roslin.ed.ac.uk

Adaptation of a commercial ELISA to determine the IgG avidity in sheep experimentally and naturally infected with Neospora caninum

Recent reports indicate Neospora caninum has a possible role in causing abortions in sheep in New Zealand. Knowledge about the epidemiology of neosporosis in sheep is limited. This study aimed to adapt and validate a commercially available ELISA assay as an IgG avidity assay to discriminate between acute (primary and re-inoculated) and chronic N. caninum infections in sheep. In addition, it was used to compare the antibody avidity values between lambs from ewes inoculated with N. caninum either during the pregnancy or in the previous year. The avidity assay was undertaken by using 6M urea for the first wash after incubation with the primary antibody in the commercial ELISA (Chekit* Neospora antibody test kit, IDEXX Laboratories, Australia). Sequential serum samples were obtained from naïve ewes (n=16) experimentally inoculated with live N. caninum tachyzoites. All ewes were seropositive by two weeks post-inoculation and remained seropositive for 20 weeks post-inoculation. There was a linear relationship between time after inoculation and avidity values (p<0.05) over the first 24 weeks. In Week 4, all animals had avidity values <35% and by Week 8, 8/16 animals had avidity values of >35%. These results suggest that an avidity value of <35% indicates a recent primary infection while a value of >35% is indicative of a chronic infection. The assay was then validated using samples from other groups of experimentally inoculated sheep as well as samples from naturally infected ewes. When comparing sample to positive ratio (S/P) and avidity values from lambs born from recently inoculated ewes with those from ewes inoculated the previous year and re-inoculated in the current year, it was possible to differentiate the lambs at 2 weeks of age. Lambs from recently inoculated ewes had low S/P and avidity values at 2 weeks of age which increased by 12 weeks of age. In comparison, lambs from re-inoculated ewes had high S/P and avidity values at 2 weeks of age, due to maternal antibody influence but values were similar to those from lambs that were born from recently inoculated ewes at 12 weeks of age. Avidity values for four naturally infected ewes were all >60% indicating chronic infection. These results suggest that the assay is able to discriminate between recent and chronic infection in sheep as well as able to differentiate lambs with maternal immunity compared to their own de novo immunity. As such it can be utilized to understand the kinetics of N. caninum infection in sheep.

Seroprevalence and risk factors associated with Chlamydophila spp. infection in ewes in the northeast of Algeria

A cross-sectional study was carried out to estimate prevalence of Chlamydophila spp. antibodies and to investigate risk factors associated with chlamydial infection in 552 ewes between March 2011 and January 2012 in the province of Constantine. Anti-Chlamydophila antibodies were detected using an indirect enzyme-linked immunosorbent assay kit in 24.5% of examined sera. Of the herds, 70.4% had at least one seropositive animal. A pretested structured questionnaire was administered in order to collect information on individual animal health and herd management practices. Chi-square analysis and multivariable logistic regression model were used to identify risk factors related to Chlamydophila seropositivity. Univariable analysis revealed 17 variables with p < 0.25 that were offered to the multivariable logistic regression model which in turn identified 12-23 months age group (OR = 5.903, 95% CI (OR) = 1.690; 20.618) and not using disinfectants (OR = 2.099, 95% CI (OR) = 1.314; 8.065) as risk factors for Chlamydophila spp. seropositivity. Moreover, occurrence of stillbirth problem (OR = 3.682, 95% CI (OR) = 1.825; 7.430) and 5-10% mortality rate in young lambs (OR = 2.584, 95% CI (OR) = 1.058; 6.310) were significantly associated with seropositivity to Chlamydophila spp. On the other hand, availability of veterinary service was identified as a protective factor (OR = 0.161, 95% CI (OR) = 0.051; 0.511).

Effects of Theileria lestoquardi Infection on Haematological and Biochemical Parameters in Experimentally Infected Desert Ewes

Effects of Theileria lestoquardi Infection on Haematological and Biochemical Parameters in Experimentally Infected Desert Ewes