Ovine anaplasmosis: in utero transmission as it relates to stage of gestation

Seventeen mature, pregnant, anaplasmosis-susceptible and 3 anaplasmosis-carrier ewes were used in Anaplasma ovis in utero transmission studies. Susceptible ewes were arbitrarily allotted to 3 groups, 4 each in groups A and C and 9 in group B, and were inoculated with whole blood from a carrier ewe. Each group was Anaplasma-exposed once during one of the thirds of pregnancy. In all ewes, resulting parasitemias were low and anemias were mild. Three carrier ewes comprised group D. Blood samples were obtained once during gestation from each fetus at various stages of development for evaluation and inoculation into splenectomized lambs. Blood obtained from neonates before nursing was also evaluated for Anaplasma presence. Parasitemia was not detected in any fetus or neonate; however, 3 of 16 splenectomized lambs inoculated with fetal or neonate blood developed acute anaplasmosis. Dams of fetuses/neonates with infective blood had been Anaplasma-exposed during their 2nd or last 3rd of pregnancy. Infective Anaplasma agents crossed the placental barrier as early as 130 days of gestation.     

Field studies on the efficacy of a long acting preparation of oxytetracycline in controlling outbreaks of enzootic abortion of sheep

The effects of long acting oxytetracycline in controlling outbreaks of enzootic abortion of ewes were studied over three consecutive years in 13 different commercial flocks. When used in the face of an outbreak the compound produced a statistically significant reduction in abortion in treated ewes when compared to untreated controls. There was, however, only a marginal difference in the overall abortion rate between treated and untreated groups of ewes in known infected flocks, where the drug was used in anticipation of an abortion storm, mainly because the abortion rate was too low in the control group. It is suggested that oxytetracycline therapy should only be used in an effort to control an actual abortion outbreak on the understanding that the treatment will not eradicate infection from the flock.     

Identification of Anaplasma spp. rickettsia isolated from horses from clinical disease cases in Poland

This study was aimed at determining the cause of the diseases in five horses exhibiting symptoms of fever, joint oedema and ataxia and thrombocytopenia. The PCR technique revealed the presence in the blood of 16S RNA Anaplasma/Ehrlichia spp. genetic material. DNA amplification with primers EHR 521 and EHR 747 gave a product with a size of 247 bp. The sequence of the PCR product obtained showed a 97.6-99.6% similarity with a sequence of a fragment of 16S RNA Anaplasma phagocytophilum, gene number EU 090186 from GenBank. Intravenous administration of oxytetracycline at a dose of 8 mg/kg of body mass for 7 days resulted in a gradual recovery.     

The effects of injectable sodium selenite on immune function and milk production in Sardinian sheep receiving adequate dietary selenium.

The aim of this preliminary study was to determine the effects of selenium (Se) injection on Se status, cell-mediated immunity (CMI), milk yield and milk somatic cell count (MSCC) of ewes fed adequate amounts of Se, and on Se status, passive immunization and CMI of their offspring. Thirty days before lambing, 36 Sardinian ewes were assigned to one of three groups. One group (NT) was not treated; a second group (BL) was given 5 mg of Se on day 30 before lambing; a third group (BLL) was given 2.5 mg of Se on day 30 before lambing and at lambing. Selenium was given intramuscularly as sodium selenite. Selenium status was assessed by measuring glutathione peroxidase activity of erythrocytes (GSHpx-E). The CMI was measured by determining the increases in double skinfold thickness after intradermal injection of phytohaemagglutinin (PHA). Compared to their NT counterparts, ewes belonging to BL and BLL groups and their offspring had significantly higher GSHpx-E (P < 0.01). The GSHpx-E values of lambs were positively related to those of their mothers (P < 0.0005). Ewes of group BL had a greater (P < 0.01) response to PHA 6 h after injection than ewes of the NT group. Lambs born to BL and BLL ewes had a greater (P < 0.0001) response to PHA 24 h after injection. Responses of ewes and lambs to PHA 24 h after injection were positively related (P < 0.05). Serum immunoglobulin at 10 days of age did not differ significantly among the three groups of lambs. Compared to the NT group, milk yield on day 70 of lactation was significantly higher in BL ewes (P < 0.05). The MSCC was not affected significantly by Se injection. Immunoresponsiveness and milk yield might represent additional and appropriate criteria to consider when re-evaluating Se requirements of dairy sheep.     

Post‐glucose load changes of plasma key metabolite and insulin concentrations during pregnancy and lactation in ewes with different susceptibility to pregnancy toxaemia

Insulin resistance during late gestation may act as a predisposing factor of ovine pregnancy toxaemia (OPT). To evaluate the insulin action on energy metabolism in ewes with different susceptibilities to OPT, intravenous glucose tolerance tests (1 mmol glucose/kg body weight) were performed in 5.6 ± 0.7 year old, slightly underfed German Blackheaded Mutton ewes [high‐risk (HR) ewes] and 2.5 year old, overnourished Finnish Landrace ewes [low‐risk (LR) ewes] during mid and late pregnancy, during early lactation and during the dry period. Plasma samples were analysed for glucose, insulin, non‐esterified fatty acids (NEFA) and β‐hydroxybutyrate (β‐HB). The glucose elimination rate and the glucose‐stimulated first‐phase insulin secretion were significantly (p < 0.05) lower in the HR, in relation to the LR group combining the data of all gestational stages. The basal rate of lipolysis was significantly increased in the HR ewes during late pregnancy, but the NEFA clearance after the glucose load was similar in both groups during all reproductive stages. Plasma β‐HB concentrations decreased only in the LR ewes after the glucose load during late pregnancy. Results indicate an insulin resistance in the HR ewes regarding the glucose utilization and the ketone body formation during late pregnancy. The insulin resistance in the HR ewes may represent one predisposing factor responsible for the susceptibility to OPT. Further scientific work is necessary to elucidate whether this insulin resistance was due to breed, age or nutritional state.     

Enhancing immunity to nematode parasites in single-bearing Merino ewes through nutrition and genetic selection

The effectiveness of protein supplementation and genetic selection to enhance the resistance of periparturient Merino ewes to infection from gastrointestinal parasites was tested in a replicated grazing experiment. One hundred and twenty ewes from lines selected for increased resistance (R) to Haemonchus contortus or at random (C) were subjected to one of the three supplement groups that provided 0 or 250 g per day cottonseed meal for 5 weeks prior to, or for 6 weeks after the start of lambing. Faecal egg counts (FEC) of R ewes were consistently lower than those of C ewes but both groups exhibited a periparturient rise in FEC. Supplementation during the pre-partum period reduced FEC and increased ewe body weight gain. The benefits of pre-partum supplementation in reducing FEC continued to be apparent up to 10 weeks after supplementation ceased. There was a strong suggestion that the benefits to parasite resistance from protein supplementation were greatest in C ewes. Wool growth rates (15%) and birth weights (5%) were greater for C ewes but differences between the lines for lamb body weight had disappeared by day 97. The greatest benefit to resistance from protein supplementation was observed when ewes were experiencing a loss of maternal body weight. Conversely, no benefits to resistance were observed when ewes had moderate (78-107 g per day) rates of maternal weight gain. These results suggest that increased resistance as a result of protein supplementation is dependent on the prevailing supply and demand for scarce nutrients such as metabolisable protein (MP). Both genetic selection and protein nutrition are effective strategies to enhance host resistance to nematode infection during the periparturient period.     

Serum non-esterified fatty acids and plasma glycerol as indicators of fat mobilization in pregnant sheep subjected to cold stress

Fifteen pregnant ewes in an open barn were kept on a constant hay diet during the whole gestation period. The ewes were shorn as usually in fall and spring. The serum non-esterified fatty acids (NEFA) and the plasma glycerol (PG) content were followed during the gestation.The body weight, NEFA and PG values were rather constant during the first 2 months of gestation (NEFA: 430 ± 175 µeq./l serum, PG: 39 ± 19 µmol/1 plasma) indicating an adequate feeding during this period. NEFA and PG showed thereafter a parallel increase and reached maximal values at the first sampling after shearing which coincided with a marked drop in environmental temperature. NEFA was then 450 % and PG about 340 % of the normal values, indicating a strong increase in fat mobilization in this period. The shearing reduces the isolation property of the fur considerably, and the ewes have to produce extra heat to maintain the normal body temperature at low environmental temperatures. The metabolic rate after shearing was estimated to have been 2–4 times the basal rate at the temperatures in the barn. This strong increase in the metabolic rate was not compensated by an increased food intake, but resulted in increased fat mobilization.     

Anaplasmosis: a regional serologic survey and oral antibiotic therapy in infected herds

A test and treatment program was conducted in northern Idaho and southeastern Washington to detect bovine reactors to Anaplasma marginale and to achieve anaplasmosis-free status in the herds tested. Of 3,920 cattle tested, 214 (5.5%) were reactors; 110 of the reactors (from 7 herds) were tested after being treated orally for 45 days with chlortetracycline or oxytetracycline at a calculated daily dosage of 11 mg/kg of body weight, and all were seronegative. Two reactors refused to eat the medicated feed and were seropositive at retest. In untreated herds, the prevalence of reactors remained constant. It was concluded that a test and treatment program would have to be continued for several years to achieve an anaplasmosis-free status in cattle herds of the area.     

Effect of five daily intravenous treatments with oxytetracycline hydrochloride on the carrier status of bovine anaplasmosis.

Intravenous administration of oxytetracycline hydrochloride at the rate of 22 mg/kg daily for 5 days was effective in rendering parasite-free 11 adult cattle that were naturally infected Anaplasma marginale carriers. The treatment did not cause any noticeable distress or side effect. Through 12 posttreatment months, the efficacy of the treatment procedure was evaluated by serologic tests and subinoculation of blood into susceptible splenectomized calves. Results of the rapid card agglutination test were positive for 5 cattle at 2 months after treatment, but negative for all cattle at 4 through 12 months. Complement-fixation titers were variable and transient in posttreatment serologic studies. After subinoculation of blood into splenectomized calves (at 4 and 12 months after chemotherapy), serologic, hematologic, or clinical evidence of infection with A marginale was not seen during a 60-day observation period.     

Morphologic alterations of Anaplasma marginale in calves after treatment with oxytetracycline.

The morphologic features of Anaplasma marginale were determined after treatment of infected calves with oxytetracycline. By light microscopy, anaplasma bodies in erythrocytes of treated calves were enlarged and vacuolated, small and dense, or comma shaped. Several degenerated forms of anaplasma bodies were observed by electron microscopy. There was a blending of the 2 membranes surrounding initial bodies, aggregation of nucleoprotein at the periphery of the subunit, and vacuolation. A 2nd form of degeneration was coalescence of subunits in marginal bodies. A 3rd form of degeneration was unification of subunits of anaplasma bodies and clumping of nucleoprotein. A 4th form of degeneration was the persistence of an anaplasma body as a solitary, irregularly shaped mass containing electron-opaque clumps.     

Effect of feed flushing during summer season on growth, reproductive performance and blood metabolites in Malpura ewes under semiarid tropical environment

Feed scarcity during hot summer months is one of the major predisposing factors for low reproductive efficiency of livestock reared in hot semiarid environment. A study was conducted to assess the effect of concentrate supplementation during summer months on growth, reproductive performance, and blood metabolites in Malpura ewes. Twenty adult Malpura ewes were used in the present study. The ewes were divided into two groups viz, group 1 (n?=?10; control) and group 2 (n?=?10; concentrate supplementation). The study was conducted for a period of 35 days covering two estrus cycles. In the first cycle, only PGF_2α was given to all ewes, while in second cycle, all ewes were synchronized for estrus using progesterone-impregnated intravaginal sponges and pregnant mare serum gonadotropin. The animals were allowed for grazing for 8–10 h per day. Apart from grazing, group 2 ewes were supplemented with concentrate mixture at 1.5 % of body weight. Concentrate supplementation had significant influence on body weight, ADG, estrus percentage, estrus duration, onset of estrus, ovulation response, plasma glucose, total protein, and urea. The present study reveals that ewes supplemented with concentrate mixture at 1.5 % of body weights during summer season significantly influenced the growth and reproductive performance of Malpura ewes. Further, the study signifies the importance of providing additional feed supplementation to ewes kept grazing under the conditions of a hot, semiarid environment to improve their reproductive efficiency.     

Effects of trichostrongyle larval challenge on the reproductive performance of immune ewes

Ostertagia circumcincta larvae were administered to adult immune ewes either during the breeding period or around parturition to investigate whether reproductive performance was affected. Two groups of 25 ewes were given water or 12,000 ostertagia larvae three times weekly for five weeks before and five weeks after breeding to synchronised oestrus. Plasma pepsinogen levels were raised in the larval-challenged ewes during the treatment period but no significant effect of treatment was observed on ovulation rate or plasma progesterone concentration. Neither ewe live-weight nor body condition score differed between groups throughout gestation or for four weeks post partum and there was no effect from larval challenge during the breeding period on lambing rate, lamb birthweight or liveweight at four weeks old. A second experiment involved 20 twin-bearing immune ewes which were administered 17,000 ostertagia larvae three times weekly for three weeks before and three weeks after parturition. Plasma pepsinogen concentration was elevated during the larval challenge period and nematode eggs were detected in the faeces after parturition but there was no effect from treatment either on ewe liveweight and body condition score or on lamb birthweight and lamb liveweight at four weeks old. These results indicate that larval challenge with ostertagia larvae at dose rates comparable to larval intake from heavily contaminated pasture did not affect the general well being and reproductive performance of immune Greyface ewes.     

Comparison of the efficacy of enrofloxacin, imidocarb, and oxytetracycline for clearance of persistent Anaplasma marginale infections in cattle

This study compared enrofloxacin and imidocarb dipropionate treatments with an oxytetracycline regimen proposed by the World Organization for Animal Health for elimination of persistent Anaplasma marginale infections in cattle. The effect of therapy on competitive ELISA and polymerase chain reaction (PCR) reactivity was also assessed. Twelve A. marginale-infected carrier calves were randomly assigned to groups receiving either enrofloxacin (5 mg/kg IV q24h for 5 days), imidocarb (5 mg/kg IM twice, 7 days apart), or oxytetracycline (22 mg/kg IV q24h for 5 days). One calf infected with an Oklahoma isolate in the imidocarb group and one infected with a Virginia isolate in the oxytetracycline group failed to infect a splenectomized calf following blood subinoculation. Both became competitive ELISA negative by 44 days after treatment, but the imidocarb-treated calf remained PCR positive. None of the tested treatments reliably eliminated persistent A. marginale infections in all cattle. Furthermore, PCR was not a reliable means of determining the success of chemosterilization in calves.     

Effects of supplementation with digestible undegradable protein in late pregnancy on ewe colostrums production and lamb output to weaning

The aim of this study was to investigate the effects of supplementation with digestible undegradable protein (DUP) in diet during late pregnancy on colostrum production, lamb survival and growth. For 3 weeks prior to lambing, 41 Afshari ewes were assigned at random to three dietary treatments, namely a control (CDUP), moderate (MDUP) and high (HDUP) DUP group. The ewes (n = 14) in CDUP group were fed a protein maintenance level for pregnant ewes [83 g metabolizable protein (MP)/kg dry matter (DM)], while ewes in the MDUP (n = 13) and HDUP (n = 14) groups were fed diets provided 14% (94.7 g MP/kg DM) and 24% (104.3 g MP/kg DM) MP in excess of these requirements respectively, which this increment was coming from DUP (DUP/MP ratio 43.8; 51.0% and 57.6% respectively). All diets were isoenergetic (12 MJ ME/kg DM). All ewes received the same lactation diet after lambing. Ewes in HDUP tend to produce more colostrums (p < 0.1) and had higher protein, fat, and solids non-fat content (p < 0.05) in colostrums during the first 24 h after lambing. MDUP group had higher colostrum yield compared to CDUP (p < 0.1). The changes in body weight and body condition score of ewes were similar for all diets but placenta weight was higher in MDUP group (p < 0.05) than for HDUP and CDUP ewes. Lamb body weight at weaning was higher for males compared to females (p < 0.05), but was not different between treatments. HDUP ewes had higher blood glucose concentration in the pre-lambing period than other treatments (p < 0.05). In this period, increasing the level of DUP in diet increased the content of blood urea nitrogen (p < 0.05). It was concluded that increasing the DUP content of diet for 3 weeks prior to lambing above the standard requirements resulted in an increase in colostrums production but had no effect on lamb outcome to weaning.     

Transplacental infection of a foal with Anaplasma phagocytophilum

This is the first report to document transplacental transmission of Anaplasma phagocytophillum in the horse. A 4-year-old late-term pregnant mare presented for a recent onset of pyrexia due to equine granulocytic anaplasmosis (EGA). She was hospitalised for treatment with oxytetracycline and monitoring of high-risk foaling due to significant thrombocytopenia. Parturition occurred overnight, and the foal was PCR positive for A. phagocytophilum at birth. The foal was slow to stand and nurse, with signs of neonatal encephalopathy and anaplasmosis (thrombocytopenia). Therapy with oxytetracycline resulted in complete clinical recovery of the mare and foal within 5 days. Congenital anaplasmosis should be considered in any foal delivered to a mare suffering from EGA during late-term pregnancy and guide appropriate antimicrobial therapy.     

Regulation of the resistance to nematode parasites of single- and twin-bearing Merino ewes through nutrition and genetic selection

Periparturient Merino ewes obtained from lines of sheep that had been selected either for increased resistance to Haemonchus contortus (R) or at random (C) were supplemented, while grazing at pasture, with either nil or 250 g/day cottonseed meal (CSM) for the 6 weeks prior to or the 6 weeks after the start of parturition. Ewes from both supplement groups had lower (mean 66% reduction) faecal egg counts (FECs) during the postpartum period and this coincided with a period of maternal body weight loss. Factors which increased the rate of maternal body weight loss, such as pregnancy and lactation status, also increased FEC. Evidence is presented that the magnitude of the periparturient rise (PPR) in FEC in grazing ewes will be greatest during periods of maternal weight loss and at these times supplementation to increase metabolisable protein (MP) supply will be most effective in increasing resistance to nematode parasites. The resistance of R ewes to nematode parasites was greater than that of C ewes throughout the experiment and was sufficiently low such that anthelmintic treatment in a commercial environment may not have been required. Irrespective of actual FEC, ewes from all treatment combinations exhibited a PPR in FEC. Reduced FEC of R ewes resulted in reduced apparent pasture larval contamination after 18 weeks of continuous grazing but supplementation was ineffective in this regard. It is suggested that integrated parasite management (IPM) programs for periparturient ewes should make use of both protein supplementation and genetic selection to increase worm resistance and reduce dependency on anthelmintics for worm control.     

Effect of mass medication with antibiotics at feedlot entry on the health and growth rate of cattle destined for the Australian domestic market

OBJECTIVE: To examine the effectiveness of mass medication with long acting antibiotics at feedlot entry on lot-fed Australian domestic cattle during a period of high risk for bovine respiratory disease (BRD). DESIGN: Systematic allocation at feedlot entry of tilmicosin, long acting oxytetracycline or no antibiotic treatment, to cattle lot fed for the Australian domestic market. Comparisons of growth rate, disease occurrence and mortality were made between the groups at the conclusion of the feeding period. RESULTS: Cattle medicated with tilmicosin at 10 mg/kg body weight on entry to the feedlot grew 0.08 kg/d faster than cattle medicated with oxytetracycline at 20 mg/kg body weight and non-medicated cattle. There was no significant difference in growth rate between oxytetracycline medicated cattle and cattle not medicated with antibiotic at feedlot entry. Cattle medicated with tilmicosin at feedlot entry had 8 fewer cases of disease per 100 animals compared with cattle not medicated with antibiotic at feedlot entry. There was no significant difference in disease occurrence between oxytetracycline medicated cattle and those not medicated with antibiotic at feedlot entry. CONCLUSION: Mass medication with tilmicosin at feedlot entry of cattle destined for the Australian domestic market may be used to reduce disease occurrence and increase growth rate during periods of high risk for BRD.     

Spread of Coxiella burnetii infection in a flock of sheep after an episode of Q fever

In October 1998, two abortions associated with Coxiella burnetii occurred in a group of 34 pregnant ewes in the sheep flock belonging to INRA Tours-Nouzilly. The flock was kept in groups of approximately 40 ewes, which were housed together in the same accommodation. The prevalence of C burnetii infection in the groups was investigated by using ELISA and PCR tests, which revealed a high prevalence of C burnetii. The ewes were treated with oxytetracycline to reduce the shedding of C burnetii and to prevent further abortions. Nevertheless, five abortions attributed to C burnetii occurred in January and March 1999 in three groups of ewes, and 24 of the ewes still shed the bacteria into their vaginal tracts. In addition, a serological study was carried out during the first year of life of the female lambs born in 1999 and 2000; 12 per cent of 113 lambs born in 1999 were seropositive for C burnetii by ELISA, and half of the ELISA-positive lambs were born either to serologically positive ewes or to dams that excreted the pathogen into their vaginal tracts. However, all the 150 lambs born in 2000 were ELISA-negative, suggesting that the preventive measures undertaken had suppressed both the abortions and the shedding of C burnetii, and reduced the transmission of the agent.     

Relative resistance of Dorper crossbred ewes to gastrointestinal nematode infection compared with St. Croix and Katahdin ewes in the southeastern United States

A study was conducted to evaluate relative resistance of Dorper crossbred (DO), Katahdin (KA), St. Croix (SC), and Hampshire (HA) ewes to natural and experimental gastro-intestinal (GI) nematode infection over a 20-month period. The objective of Experiment 1 was to evaluate breeds for resistance to infection acquired naturally from mixed grass pastures. In Year 1 (May-December 2000) de-worming of ewes occurred during wet, hot conditions in July and during late pregnancy in December. In Year 2 (January-December 2001), ewes were de-wormed after fecal egg count (FEC) for a breed group rose above 1000 eggs per gram (epg) or after blood packed cell volume (PCV) of an individual ewe fell below 20. FEC was determined every 28 days and PCV every 14-28 days. In both the years, ewes were pastured together, except during the 28-days breeding periods, on tall fescue, bermudagrass, or ryegrass, and rotated among pastures dependent on forage availability. Ewes were in good or excellent condition (body condition score of 3-4 out of 5) throughout the study. The objective of Experiment 2 was to evaluate the breeds for relative resistance to an experimental infection with Haemonchus contortus infective larvae. Both PCV and FEC were determined every 7 days from 14 to 42 days after inoculation with 30000 infective larvae per ewe. In Experiment 1, Year 1, FEC was slightly greater and PCV was lower from July to September in DO ewes (breed x time, P<0.001). In Year 2, de-worming occurred 14 days later in DO ewes compared with other breed types. Otherwise PCV and FEC were similar among the hair breeds and higher and lower, respectively, compared with HA ewes (breed x time, P<0.001). In Experiment 2, FEC and PCV were similar among hair breeds; FEC was lower and PCV higher in hair breeds compared with that of HA ewes (P<0.01). Relative resistance of mature Dorper crossbred ewes was comparable to that of Katahdin and St. Croix ewes and superior to that of Hampshire ewes.     

Induction of ovarian cystic follicles in sheep

Cystic follicles are a significant cause of infertility in women, dairy cattle and sheep. Sheep were used as a model to identify factors that may elicit formation of cystic follicles. Insulin resistance and elevated LH activity were tested in overweight ewes because of associations among these factors and the formation of cystic follicles. Sheep were synchronized using a progesterone-releasing pessary and insulin resistance was induced during the synchronization period through administration of bovine somatotropin. Following removal of pessaries follicular growth was stimulated by treatment with eCG or eCG and hCG (PG-600). Follicular growth was monitored via daily transrectal ultrasonography and blood samples were collected for hormonal analyses. Six of 18 ewes had a subnormal or absent preovulatory gonadotropin surge and developed cystic follicles. Neither insulin resistance nor elevated LH activity were associated with formation of cystic follicles. Ewes that developed cystic follicles were heavier (93 +/- 4 kg) than ewes that ovulated (81 +/- 3 kg; P = 0.02). Furthermore, following pessary removal and initiation of daily ultrasonography, ewes that developed cystic follicles lost body weight (-3 +/- 1%), while ovulatory ewes continued to gain body weight (1 +/- 1%; P = 0.005). It is speculated that in heavy ewes metabolic factors associated with acute body weight loss inhibit the positive feedback of estradiol and thereby suppress the preovulatory gonadotropin surge leading to formation of cystic follicles.