Identification of an immunodominant 40 kDa merozoite antigen common to the Australian T and Dixie vaccine strains of Babesia bovis and the development of diagnostic tests specific for these strains

Antigenic differences among Australian vaccine and field strains of Babesia bovis were investigated in an attempt to identify strain specific antigens. Immunoblots revealed substantial differences between the current vaccine strains, designated T and Dixie, and previous vaccine strains and field isolates collected on properties where vaccination with the T or Dixie strains had failed to provide complete protection against tick-borne challenge. A major difference was an immunodominant 40 kDa antigen (T40) present in only the T and Dixie strains. The molecular weight and immunodominant nature of this antigen suggest that it may be the equivalent of the major merozoite surface antigen (MSA-1) described by others in North American strains of B. bovis. MSA-1 was shown to be conserved in north American isolates but not in an isolate from Israel or in the Australian S and L isolates. The work presented here suggests that merozoite surface antigen diversity exists among geographically different isolates of B. bovis within Australia.

Monospecific antiserum to T40 was used to develop an indirect fluorescent antibody (IFA) test specific for T and Dixie strain parasites, and a blocking enzyme-linked immunosorbent assay (ELISA) specific for antibody to the T and Dixie strains. In cases of babesiosis in recently vaccinated cattle, the IFA test will be a useful tool for determining whether clinical symptoms are due to a severe vaccine reaction or to a concurrent tick-borne infection. In a preliminary assessment of potential of the ELISA for the serological identification of vaccinated cattle using a total of 160 sera, the test clearly differentiated between animals vaccinated with the T or Dixie strains and non-vaccinated animals, and was not affected by presence of antibodies to other B. bovis strains.     

Evaluation of an enzyme-linked immunosorbent assay kit to detect Babesia bovis antibodies in cattle

The sensitivity and specificity of an enzyme-linked immunosorbent assay (ELISA) to detect antibodies; to Babesia bovis was evaluated in 1000 sera from Holstein heifers. Five hundred of them were from cattle naturally or experimentally infected with B. bovis and 500 from uninfected heifers born and raised in a region free of the vector of cattle babesiosis. Additionally, the ELISA was evaluated and compared with an indirect immunofluorescent antibody (IFA) test in 374 heifers inoculated with different kinds of B. bovis antigens in four trials. The cross-reaction was also evaluated in 50 heifers infected with Babesia bigemina and 50 heifers infected with Anaplasma marginale. The mean percentage positivity of negative sera in relation to the ELISA strong positive sera was 8%. The seropositive/seronegative cutoff point was set as twice the mean percentage positivity of negative cattle sera ( = 16%). The sensitivity of the ELISA was 98% with a 95% confidence interval (CI) of 96–99%. The specificity was 95% (CI 93–97%). The agreement was 97% and the kappa value was 0.93. The predictive values of positive and negative results were 95% and 98% respectively. ELISA showed a similar sensitivity to that of the IFA test to detect antibodies to different B. bovis antigens. Its sensitivity ranged from 97.1% to 100% (CI 89–100%), while the sensitivity of the IFA test ranged from 92.8% to 100% (CI 83–100%). ELISA cross-reacted in 8% and 6% of the sera carrying B. bigemina and A. marginale antibodies, respectively, while the IFA showed 4% cross-reaction in each situation. The ELISA evaluated has the advantages of a proper sensitivity, objectivity and capacity to be adapted to test large number of samples in a short period of time. The results indicate that the ELISA is a suitable replacement for the IFA test to detect B. bovis antibodies in cattle sera, especially in epidemiological studies.     

Clinical and serological evidence of bovine babesiosis and anaplasmosis in St. Lucia

One hundred fifty-nine Holstein calves were imported into St. Lucia from the U.S.A. An outbreak of babesiosis occurred 17 days post-arrival, and an outbreak of anaplasmosis occurred 5 months after importation. Sera obtained 3, 6 and 12 months post-importation revealed a high prevalence of IFA titres to Babesia bovis and B. bigemina 3 months after arrival and an increase in titres to Anaplasma marginale 6 months after arrival. Sera obtained arrives from native cattle from several places on the island indicated infection rates of 80, 65 and 64% with A. marginale, B. bigemina and B. bovis, respectively. The rapid card test only indicated a 25% prevalence of infection of native cattle by A. marginale. This low prevalence was probably due to deterioration of serological activity during shipment.     

Management factors associated with Babesia bovis seroprevalence in cattle from eastern Yucatán, Mexico.

The effect of management on the seroprevalence of Babesia bovis was studied in 399 Bos indicus cattle 1–2 years old from 92 farms in the eastern Yucatán, México. The management factors studied were: farm-type, production system, herd size, farm size, stocking density, vector control, dipping interval, type of dipping, type of acaricide and cattle introduction to the farm. A cross-sectional study was carried out (2-stage cluster sampling). The number of serum samples was proportionally distributed according to the number of farms in the nine locations of eastern Yucatán, México (399 animals from 92 farms). Antibody activity to B. bovis was tested using an indirect ELISA. The farms with a seroprevalence ≤75% were considered as cases and those with seroprevalence >75% were considered as controls. The variables with p ≤ 0.20 were included in fixed effects logistic regression. The seroprevalence of the zone was 73.8% (66.3–81.3%). The following risk factors were found: Stocking density (<1 head/ha, OR = 4.04, CI (OR) = 1.20–13.62) and dipping interval (>60 days, OR = 5.07 CI (OR) = 1.26–20.48).     

A study of an enzootic focus of sheep babesiosis (Babesia ovis, Babes, 1892)

Morbidity and mortality due to Babesia ovis in sheep flocks grazing in an enzootic area of Israel occur yearly, about 2 weeks after detection of adult Rhipicephalus bursa ticks on the animals. Disease incidence peaks in May, but lasts throughout the active period of the adult ticks in the spring-summer months of April–July. No clinical cases of babesiosis have been registered during the active period of the preimaginal stages of R. bursa, from October to February. Incidence of parasitaemia during the spring-summer months was variable, ranging between 2 and 25%. However, in the winter months the incidence of parasitaemia in hoggets increased considerably, reaching 4–60% of the animals.

A positive serological response to B. ovis was found in 84.5% of the hoggets and 88.9% of the ewes. In ewes, the prevalence of the serological response showed no marked seasonal variations. Colostral sera of 67.5% and 75% of the ewes and hoggets, respectively, were serologically positive for B. ovis. No antibodies were detected in the sera of lambs less than 3–4 months of age. The epizootiology of sheep babesiosis appears to differ from that of bovine babesiosis.     

Study on some molecular characterization of Babesia orientalis

The study on buffalo babesiosis indicated that its pathogen was different from other Babesia on many aspects such as morphology, transmission and pathogenicity. Therefore, it was named as a new species—Babesia orientalis. In order to prove the validity of this taxon, molecular taxonomic study on the pathogen was done in this experiment. The complete 18S rRNA gene sequence of B. orientalis was determined by PCR. It was sequenced and blasted. The results indicated that the classification of the parasite belonged to the genus Babesia. The 1700 bp complete sequence was compared with 15 other Babesia sp. available in GenBank. The data were analyzed and a phylogenetic tree was established. The results indicated that the hereditary distance of the parasite was close to that of Babesia sp. from South Africa and Babesia ovis, and the hereditary distance was far from Babesia bigemina and B. bovis.     

Effect of agro-ecological zone and grazing system on incidence of East Coast Fever in calves in Mbale and Sironko Districts of Eastern Uganda

Between May 2002 and February 2003 a longitudinal survey was carried out in Mbale and Sironko Districts of Eastern Uganda to determine the influence of agro-ecological zones (AEZ) and grazing systems on tick infestation patterns and incidence of East Coast Fever (ECF) in bovine calves. The study area was stratified into AEZ (lowland, midland and upland) and grazing systems {zero grazing (ZG), restricted-outdoor grazing (ROG) and communal grazing (CG)}, whose strata had previously been shown to influence the prevalence of ECF, babesiosis and anaplasmosis. One hundred and eighty-five smallholder dairy farms with a total of 198 calves of both sexes, between the ages of 1 day and 6 weeks, were purposively selected from the AEZ–grazing system strata. Nine dynamic cohorts (11–51 calves in each) of these calves were examined and sampled monthly. Ticks infesting the calves were counted from one side of the animal body and categorized into the different species, sex and feeding status. Sera were collected at recruitment and monthly thereafter and antibodies against Theileria parva, T. mutans, Babesia bigemina, B. bovis and Anaplasma marginale were measured using ELISA. Tick challenge (total and specific) varied with AEZ and grazing system. The risk of infection with T. parva was higher in the lowland zone compared to the upland zone (hazard ratio (HR) = 2.59; 95% CI: 1.00–6.34). The risk of infection with T. parva was higher in the CG system than the ZG system (HR = 10.00; 95% CI: 3.61–27.92). The incidence risk for sero-conversion, over the 10 months study period, was 62, 16 and 9% in the lowland, midland and upland zones, respectively. Ninety-eight percent of the calves in lowland-CG stratum sero-converted by the age of 6 months, while 56 and 8% did so in the lowland-ROG and the lowland-ZG stratum, respectively. The results of this study show the need to consider farm circumstances and the variation in ECF risk, both spatially and temporally when designing control strategies for ECF.     

Simulation model of within-herd transmission of bovine tuberculosis in Argentine dairy herds

Transmission of bovine tuberculosis was quantified in three dairy herds located in south Santa Fe Province, Argentina. Using estimates of Mycobacterium bovis transmission (β) and a Reed–Frost simulation model, the prevalence of tuberculosis infection in the study herds over time was investigated. The Reed–Frost model was modified by incorporating randomness in both β and the incubation period () of M. bovis. The mean estimated herd β was 2.2 infective contacts per year and did not differ significantly between the study herds. Modeling as Poisson distributed (mean 24 months) best fit the observed prevalences. Infection was predicted by the model either to spread quickly (<10 years) within a herd and reach a high prevalence (>50%), or to persist at a low prevalence (<5–10%). The model was robust, predictions were realistic and the mean β estimated was consistent with previous studies of bovine tuberculosis.     

Economic evaluation of the production impact of bovine schistosomiasis and vaccination in the Sudan

This study was done to evaluate the estimated economic consequences of the recent discovery that an irradiated Schistosoma bovis vaccine was effective in reducing mortality and intensity of infection in cattle after field exposure to S. bovis in the White Nile province. The benefits and costs were hypothesized to occur over a 5-year period starting after the vaccine had been further developed to optimal commercial usefulness.

The potential benefits of vaccination are from the avoidance of mortality and growth delay losses caused by S. bovis infection and were based on an owner survey conducted in 1981. These benefits were discounted from the time of their potential marketing opportunity to the first year of a vaccination program at 15% per annum and were valued on a basis of 1982 prices for live cattle exported to Egypt and Saudi Arabia. Variations in benefits stem from degree of infection probability, mortality and morbidity estimates and percent of animals vaccinated. Since clinical schistosomiasis (“gorag” — sunken-eyed appearance) and associated production losses occur almost exclusively in 6- to 30-month-old cattle, and there is evidence for long-term immunity, vaccinations would be given to cattle in this age-specific group or younger once in their lifetime. The principal variation in vaccination program costs, also valued at 1982 prices, is from vaccine production costs; $0.50 or $4.00 per dose. A vaccine efficacy of 70%, observed in a previously reported field trial, was used in these calculations.

Present value benefit—cost (b–c) ratios were estimated for the central, western and southern areas for high- and low-level effects of S. bovis impact on production and the vaccination program, cost and effectiveness. In an area (central provinces) of high infection probability (90%), high percentage of animals vaccinated (90%), high mortality (7.1%), and low vaccine production costs, the b–c ratio was 12.7. In contrast, a b–c ratio of 0.7 was estimated for an area (southern provinces) assuming low infection probability (50%), low percent of animals vaccinated (50%), lower mortality (3.55%) and high vaccine production costs. Potential returns from increased future milk and calf production and from faster herd build-up with younger females were not included in these benefit calculations. These results indicate that under most conditions further development of the vaccine and cost-effective vaccine production techniques would yield very favorable returns from improved livestock production efficiency in the Sudan. Export prices were assumed to not vary significantly with increased supply of export-quality cattle resulting from the estimated production losses avoided by vaccination against schistosomiasis.     

A study on Theileria parva bovis carrier state

In two trials, Theileria parva bovis (which causes ‘January disease’ of cattle in Zimbabwe) produced a carrier state, over the 7–12 months after infection. Very severe clinical reactions were caused by infections from small numbers (29–43) of adult Rhipicephalus appendiculatus ticks, which had engorged on immunized cattle in the field. The transmission from healthy recovered cattle housed indoors was less efficient, even with high numbers of ticks (300). Two out of seven attempts were successful and disease reactions were rather severe. A non-pathogenic Theileria assumed to be Theileria taurotragi was transmitted in three out of seven attempts.     

Evaluation of MPB70, bovine PPD and lipoarabinomannan as antigens in ELISA for the serodiagnosis of bovine tuberculosis

The performance of the secretory protein MPB70 of Mycobacterium bovis, bovine PPD, and lipoarabinomannan (LAM) were evaluated as antigens in ELISA for detection of tuberculosis (TB) infected cattle. Sera were from 120 M. bovis infected cattle and 223 cattle from a TB free herd. ELISA results were analyzed using receiver operating characteristic (ROC) curves in relation to culture results. The areas under the three ROC curves were 71 ± 49% SE (MPB70), 71 ± 27% SE (bovine PPD), and 56 ± 4% SE (LAM).     

Evaluation of an ELISA for detection of antibodies to Babesia bovis in cattle in Australia and Zimbabwe

An enzyme-linked immunosorbent assay (ELISA) for antibodies to Babesia bovis was evaluated in comparison with the indirect fluorescent antibody test (IFAT) in Australia and Zimbabwe. Positive and negative threshold values for the ELISA were set using sera from cattle of known infection status. Sensitivity and specificity estimates for the ELISA based on 158 positive sera from cattle experimentally infected with Australian isolates of B. bovis and 318 negative sera collected from B. bovis-free herds in Australia were 100% and 99.4%, respectively. The specificity of the assay in Africa, based on 328 sera from B. bovis-free herds in Kenya and South Africa, was 99.7%. The ELISA was compared with the IFAT using sequential sera from 16 calves experiencing primary B. bovis infections, and a total of 777 field sera collected from B. bovis-endemic herds in Australia and Zimbabwe. In primary infections, the ELISA and IFAT detected antibodies at or about the same time. With sera from endemic herds, the performance of the ELISA was at least comparable with that of the IFAT. Two hundred and fourteen of 221 sera that were negative by IFAT, were negative by ELISA, and 428 of 439 sera that were clearly positive by IFAT were positive by ELISA. Of 117 sera that gave equivocal (suspect or weak positive) results in the IFAT, 20 were positive by ELISA, 7 were suspect and 90 were negative. We conclude that the ELISA will be useful for epidemiological studies on B. bovis in Australia and Zimbabwe, and probably elsewhere.     

Effects of challenge dose on the clinical and immune responses of cattle vaccinated with reduced doses of Brucella abortus strain 19

Fifty-seven pregnant beef heifers that were unvaccinated or previously vaccinated with Brucella abortus S19, at a dose of either 10⁹ or 10¹⁰ colony-forming units (CFU), were challenge-exposed intraconjunctivally with virulent B. abortus S2308 at a dose of 9.4 × 10⁶ CFU (Experiment 1) or 5.2 × 10⁷ CFU (Experiment 2). In Experiment 1, S19 afforded significant protection (P < 0.01) against challenge exposure in that 8 of 9 unvaccinated heifers, 1 of 11 vaccinated with 10⁹ CFU, and 3 of 10 vaccinated with 10¹⁰ CFU aborted or delivered weak, non-viable calves. In Experiment 2, vaccination did not afford significant protection (P> 0.05) in that 9 of 9 unvaccinated heifers, 8 of 10 vaccinated with 10⁹ CFU, and 8 of 8 vaccinated with 10¹⁰ CFU aborted. Serologic responses to B. abortus were determined by three standard tests, as well as a quantitative fluorometric immunoassay (FIAX) and an enzyme-linked immunosorbent assay. In Experiment 1, the early serologic response, 0–8 weeks after challenge, appeared greater for controls than for vaccinates, but in Experiment 2, the early response, 0–6 weeks after challenge exposure, appeared greater for vaccinates than for controls. The lymphocyte blast transformation assay, using heat-killed B. abortus as an antigen, was performed sequentially after challenge exposure. In general, mean responses were significantly higher (P < 0.05) for vaccinated than for non-vaccinated heifers. For individual heifers, an association could not be established between the lymphocyte blast transformation assay and the clinical response to challenge exposure.     

Serological reactivity to Mycobacterium bovis protein antigens in cattle.

The serological response to 12 purified Mycobacterium bovis antigens were examined in an ELISA assay. These antigens included the majority of M. bovis protein antigens described to date and in most cases they were very similar to the M. tuberculosis antigens of the same molecular mass.

The purified antigens were tested against sera from M. bovis infected cattle, M. bovis culture-negative cattle from infected herds and animals infected with related microorganisms, mainly other mycobacterial species. All the antigens gave strong reactions with at least some sera from the M. bovis infected group and showed cross-reactivity with some of the sera from the other two groups. The antigen with the highest specificity reacted strongly with only 60% of the M. bovis infected sera. Antigens that reacted with most or all of the M. bovis infected sera also gave the highest cross-reactivity with sera from the other two groups. These results indicate that a serological test based on any one or a combination of these antigens, without removal of the cross-reacting epitopes, would be unsatisfactory.     

Responses of female lambs to Rev-1 (brucellosis) vaccination

In order to investigate Rev-1 vaccination immunogenicity, 60 indigenous (Makuii) non-infected female lambs 3–4 months of age in northwestern Iran were systematically divided into two groups: 40 into a treatment (T) group and 20 into a control (C) group. Lambs in Group T received 1 ml of Rev-1 vaccine by s.c. injection and blood samples were collected from both groups at 15 days and 2, 4, 6, 8, 10, 12 and 14 months after vaccination. The seroagglutination test (SAT) and the 2-mercaptoethanol test (2-MET) were carried out on the sera. Control lambs were negative in all the examinations. The results of the SAT showed that the mean( ± SD) antibody titre of lambs in Group T was maximum (725 ± 112 IUml⁻¹) at Day 15, then declined gradually until the fourth month and was in the normal range (31 IU ml⁻¹) thereafter. The results of the 2-MET were negative in Group C but in Group T the antibody titre was at a maximum level (161.7 ± 46.6 IUml⁻¹) at Day 15, decreased to 1.2 ± 2.5IUml⁻¹ at 4 months post-vaccination and was negativ; thereafter. In the second part of the trial, 20 vaccinated and ten control lambs received 0.25 ml melitin by i.d. injection 10.5 months after vaccination. The control group showed no reaction but 13 (65%) of the vaccinated lambs showed an oedematous swelling at the site of injection within 48 h, which indicated that the delayed-type hypersensitivity test (DTHT) could be useful in the diagnosis of Brucella infection in lambs. In the third stage of the experiment, four vaccinated and three control lambs were injected with Brucella melitensis strain 16M at a rate of more than 123 × 10⁶ bacteria per lamb 14 months after vaccination. Rectal temperature (Tem), heart-rate (HR) and respiration rate (RR) were measured three times a day (at 08:00, 14:00 and 21:00 h) 3 days before until 9 days after injection. SAT was carried out on the day before injection and at the time of slaughter. The mean Tem, HR and RR did not significantly change but the mean( ± SD) SAT titre in the T lambs 9 days after injection was 47.5 ± 9.9 IU ml⁻¹ (vs. 8.66 ±6.1 IU ml⁻¹ in the control lambs) (P < 0.01). All lambs were slaughtered on the ninth day. Fewer bacterial cultures of samples taken from the uterus, spleen, liver and lymph nodes were positive in T lambs compared with the controls. The lower proportion of Brucella-positive lambs in the vaccinated group compared with the control group indicates that vaccination with Rev-1 improved the resistance of lambs to the experimental infection.     

Endotoxin induces delayed ovulation following endocrine aberration during the proestrous phase in Holstein heifers

The effect of endotoxin on follicular growth and on secretion of LH, estradiol-17β, progesterone and cortisol during the proestrous phase in cattle was investigated. Holstein heifers were treated with PGF₂ at 11–13 d after ovulation to induce luteolysis. At 42 hr after PGF₂ treatment, heifers were administered either lipopolysaccharide (LPS; Escherichia coli, O111:B4, 5 μg/kg, n = 6) or saline (control; n = 6) by i.v. bolus injection. Ovarian structures were monitored daily by transrectal ultrasonography, and blood samples were collected at various times for hormonal analysis. The duration from PGF₂ treatment to ovulation was significantly longer in the LPS group (8.0 ± 1.3 d) than in the control group (4.2 ± 0.2 d). LPS significantly reduced the pulse frequency of LH for 6 hr after the administration, and increased the mean concentration and pulse amplitude of LH from 3 to 6 hr after the administration. The plasma concentrations of progesterone and cortisol were transiently increased after LPS administration. The plasma concentration of estradiol-17β was significantly decreased at 24 hr after LPS administration compared to that in the controls. Five of six LPS-treated heifers exhibited no preovulatory LH surge until 120 hr after PGF₂ treatment and the remaining heifer exhibited the surge at 108 hr after PGF₂ treatment, while the LH surge was observed at 54–78 hr after PGF₂ treatment in control heifers. These results suggest that endotoxin disrupts progression of the proestrous phase of cattle, interrupting the preovulatory estradiol rise and thus delaying the LH surge and the subsequent ovulation.     

Epidemiological aspects of canine babesiosis in the semiarid area of the state of Minas Gerais, Brazil

Epidemiological aspects of Babesia vogeli infection were studied in the canine population of a rural town located in the Brazilian “Drought Polygon” of the state of Minas Gerais, Brazil. The survey was carried out in March 2003, when 505 dogs were identified and their characteristics registered on appropriate forms. Blood samples were collected at this time and again in June, September and December 2003. Serum samples were tested by the indirect fluorescent antibody test (IFAT) to detect antibodies against B. vogeli. The prevalence of anti-B. vogeli antibodies was 18.8%; however, no correlations were found between prevalence of infection and the age or gender of the animals. Cross-bred dogs presented a higher chance of acquiring infection in comparison to pure-bred dogs. Significant differences concerning the incidence of the disease were found during the period April–June in comparison to other months, demonstrating that transmission of B. vogeli is related to seasonal variations of tick infestations. The results indicate that climatic factors within the semiarid area interfere directly in the epidemiology of canine babesiosis.     

Further data to the aetiology, pathogenesis and therapy of infectious bovine keratoconjunctivitis

Out of a total of 224 bovine eye secretions, 126 Moraxella bovis and 64 Neisseria ovis strains were isolated. The pathogenesis and histological lesions caused by Neisseria ovis have been studied on the eyes of three calves naturally affected with IBK, using electron microscopy.

Neisseria ovis caused in 1–12 weeks old calves acute, transient and mostly benign serous conjunctivitis with only slight affection of the cornea. More rarely erosions and even ulceration of the cornea have been observed.

Moraxella bovis and Neisseria ovis strains proved nearly unanimously sensitive in vitro to chloramphenicol, neomycin, oxytetracyclin, nitrofurantoin, erythromycin and cefoperazone. Other antibiotics and chemotherapeutics inhibited the growth of these agents only partly or were ineffective.

Experimental therapy has been carried out using a single i.m. injection of Terramycin/LA inj. (Pfizer) in a dose of 20 mg/kg body mass, repeated if necessary after 72–96 h. This formulation proved more effective and practical than treatments used earlier.     

甘肃榆中县奶牛球虫病流行病学调查与虫种鉴定

奶牛球虫病呈世界性分布,中国部分省市也有报道,但是甘肃省至今尚未有关于奶牛球虫病的相关调查。甘肃省榆中县是甘肃省奶牛主产区之一,为了解甘肃省榆中县奶牛球虫感染情况,对当地6个规模化奶牛养殖场1岁以内荷斯坦奶牛犊牛球虫感染情况进行了调查。试验采用显微镜下观察的方法检测了该地区的234份奶牛粪便样品,并对球虫阳性粪便进行重铬酸钾法孵化来鉴定球虫种类。结果发现,犊牛球虫总感染率达到46.15%,其中1~3月龄犊牛平均感染率为52.43%,4~6月龄犊牛平均感染率为37.50%,7~12月龄犊牛平均感染率为43.37%。经虫种鉴定,共发现7种艾美尔属球虫和1种等孢属球虫,7种艾美尔属球虫分别是牛艾美尔球虫(Eimeria bovis)、奥博艾美尔球虫(Eimeria auburnensis)、邱氏艾美尔球虫(Eimeria zuernii)、阿拉巴艾美尔球虫(Eimeria alabamensis)、亚球形艾美尔球虫(Eimeria subspherica)、椭圆艾美尔球虫(Eimeria ellipsoidalli)、加拿大艾美尔球虫(Eimeria canadensis),其中牛艾美尔球虫、奥博艾美尔球虫、邱氏艾美尔球虫为优势种。本次调查结果表明,甘肃省榆中县奶牛球虫感染情况严重,应引起相关部门重视。     

Epidemiologic Survey and Species Determination of Coccidia Infection in Dairy Cattle in Yuzhong,Gansu Province

This investigation aimed to examine coccidia infection in diary cattle in Yuzhong,Gansu province.An investigation was carried out on the Holstein calves less than one year old in six large-scale dairy farms.A total of 234 fecal samples were examined,and oocysts were identified to the species level on the basis of morphological features after positive samples were mixed thoroughly with 2.5% potassium dichromate solution.The results showed that the prevalence rate of coccidia in Holstein calves reached 46.15%.The average prevalence rate of the calves under 3 months old was 52.43%,the 4 to 6 months old calves was 37.50% and the 7 to 12 months old calves was 43.37%.Seven species of Eimeria coccidians and one species Isospora sp.including Eimeria bovis,Eimeria auburnensis,Eimeria zuernii,Eimeria alabamensis,Eimeria subspherica,Eimeria ellipsoidalli,Eimeria canadensisi,were identified in the investigation,and Eimeria bovis,Eimeria auburnensis,Eimeria zuernii were the dominant species.In conclusion,the prevalence rate of coccidiosis in dairy cattles in Yuzhong,Gansu province was high.Therefore,appropriate strategies and measures should be taken to control coccidiosis prevalence in dairy cows in this region.