Tick-borne parasitic diseases in cattle: current knowledge and prospective risk analysis related to the ongoing evolution in French cattle farming systems

Parasitic diseases, like babesiosis and theileriosis are transmitted by ticks: their occurrence is therefore linked to the size of the tick stock and the seasonality of the vectors. Babesia divergens bovine babesiosis transmitted by Ixodes ricinus is widespread and often reported in France. Serological prevalence is high, ranging from 20 to 80% according to the farms. Clinical incidence is low: around 0.4% for the whole cattle population. The endemic situation is unstable and clinical cases occur more frequently with farming system modifications. L. ricinus is a tick essentially found in woodlands and so, for the most part, is found in closed rural areas. The situation of the other bovine babesiosis (Babesia major) and theileriosis (Theileria orientalis) is not well documented in France. However, the epidemiology of parasitic diseases is changing, especially because of changes in the environmental characteristics, i.e. both farm and herd management conditions and also climatic conditions. These modifications can provoke an increase in the tick stocks, an increase in the contact rate between cattle and ticks, and an increase in the contact rate between cattle and the wild fauna, especially deer. This results in likely modifications of the endemic situation, with a higher risk of clinical babesiosis in the medium term.     

Annual evolution of cattle immunity against Babesia divergens in Northern Switzerland

A seroepidemiological survey of Babesia divergens babesiosis was conducted on 9 farms in a focus of northern Switzerland (Clos-du-Doubs, Jura). During 1981, a total of > 300 cattle were examined for B. divergens antibodies with an indirect immunofluorescence test. Annual evolution of immunity was estimated 3 times during the year (April, July and December). Cattle were progressively sensitized against B. divergens during the grazing period. Considering all cattle, 33.9% possessed anti-B. divergens antibodies in spring, before the grazing period. This percentage increased in the summer (59.1%), reaching 90.6% in December.In the studied area, the most important calving period occurs in autumn and young calves do not leave the farm before they are 2 months old. Calves generally lacked maternal antibodies when they were moved to pastures for the first time. Although infested with B. divergens-infected ticks, they never presented acute symptoms of babesiosis. They appeared to be naturally resistant to the disease. Cattle from 9 months to 3 years old were more susceptible. In April, 73.4% did not show antibodies. During our study, 12 of the 15 cattle of that age which had babesiosis did not possess antibodies. Cattle > 3 years old were more protected. In April, only 51% lacked antibodies and 1 case of babesiosis was observed in this group.     

Isolation of Babesia divergens from carrier cattle blood using in vitro culture

Babesia divergens, the main causative agent of bovine babesiosis in Western Europe, was isolated from naturally infected cattle. Ninety-six blood samples were examined by means of an in vitro culture technique in sheep erythrocytes: 19 of them were collected from animals in the acute phase of the disease with visible parasitemia on blood smears, while the 77 remaining animals showed no microscopically detectable parasites. B. divergens was cultured from the 19 first blood samples as well as from 31 samples collected from asymptomatic animals. The time period before parasites could be detected in the culture varied in the latter samples from 6 to 20 days. The effects of sampling condition (anticoagulant used) and storage length were tested. A good correlation was obtained between immunofluorescent antibody test and culture, with identical results (positive or negative) for 89.6% of the samples collected from asymptomatic animals. The sensitivity of the in vitro culture method was determined and was about 10 parasites/mL of whole blood from three independent experiments performed with three different isolates, confirming its suitability to detect and culture diverse B. divergens isolates from carrier cattle. The parasites could indeed be isolated 9 months after the acute babesiosis phase in the blood of naturally infected animals. The 50 isolates collected in this study were successfully subcultured, cryopreserved and resuscitated using the same culture medium. The in vitro isolation of B. divergens from asymptomatic carrier cattle was achieved and will allow the analysis of parasite diversity within cattle herds.     

Inhibition of Babesia divergens in cattle by oxytetracycline

The effects of continuous oxytetracycline administration on the development of parasitaemia of Babesia divergens during both natural and artificial infections were studied. During natural exposure on grazing heavily infested with Ixodes ricinus, seven out of 42 cattle with no previous exposure to tick-borne diseases were injected every four days with a long acting preparation of oxytetracycline at a dose rate of 20 mg/kg. During the six week grazing period 21 untreated cattle developed a patent parasitaemia of B divergens and all became seropositive by the fluorescent antibody test. In contrast, no parasites were observed in treated cattle and antibody titres remained low. Artificial infections were studied with different dose levels of oxytetracycline and their effects on antibody stimulation noted. First, four groups of cows were infected with 10(8) erythrocytes infected with B divergens, three groups being injected every four days with the long acting oxytetracycline formulation at dose levels of 20, 10 and 5 mg/kg, respectively. The highest level completely inhibited parasite replication and antibody formation; the same was observed in one animal dosed at 10 mg/kg but the remainder, plus those treated at 5 mg/kg, developed both low parasitaemia and high antibody titres. The untreated cows developed severe babesiosis. A further untreated control group was added and three weeks after cessation of oxytetracycline treatment all were infected with 10(9) erythrocytes infected with a homologous isolate of B divergens. The controls, plus those in which the previous infection had been completely inhibited, developed severe clinical babesiosis but the remainder were refractory to parasite development.     

Modelling bovine babesiosis: a tool to simulate scenarios for pathogen spread and to test control measures for the disease

Tick-borne diseases are of increasing concern in many countries, particularly as a consequence of changes in land use and climate. Ticks are vectors of numerous pathogens (viruses, bacteria, protozoa) that can be harmful to humans and animals. In the context of animal health, bovine babesiosis poses a recurrent threat to cattle herds. In this study, we use a modeling approach to investigate the spread of babesiosis and evaluate control measures. A previously developed tick population dynamics model (here, Ixodes ricinus) is coupled with a pathogen spread model (here, the protozoan Babesia divergens), which describes pathogen spread in a dairy herd through the following processes: transmission, acquisition, transovarial transmission, transstadial persistence, and clearance of the pathogen. An assessment of the simulated B. divergens prevalence levels in ticks and cattle in the context of existing knowledge and data suggested that the model provides a realistic representation of pathogen spread. The model was then used to evaluate the influence of host density and the effect of acaricides on B. divergens prevalence in cattle. Increasing deer density results in an increase in prevalence in cattle whereas increasing cattle stocking rate results in a slight decrease. A potential increase in deer density would thus have an amplification effect on disease spread due to the increase in the number of infected ticks. Regular use of acaricides produces a reduction in pathogen prevalence in cattle. This model could be adapted to other tick-borne diseases.     

Epidemiological study of the prevalence of Babesia divergens in a veterinary practice in the mid-east of France

To assess the epidemiology of Babesia divergens in a veterinary practice based in the mid-east of France ("Monts du Lyonnais"), blood was collected from 254 cattle belonging to 24 herds. To assess the dynamics of the carrier state, six carriers were identified, treated with flumethrin and sampled once every 3 weeks during 6 months. Two different DNA extraction methods were compared. Each sample was tested for the presence of parasites using a PCR-RFLP test based on the 18S rRNA gene. The sensitivity of the test was equivalent to a parasitaemia as low as 10(-5)% (in "Filter Paper" samples) and 10(-6)% in 1 ml blood (extracted using "Matrix"). With the latter method, the rate of detection diminishes in the low parasitaemia range but could probably be improved. This test proved to be very useful in the detection of B. divergens carriers. Serology using IFAT showed 7% of the cattle seropositive, which is suggestive of a disease situation with a low clinical risk level. Analysis of the PCR results suggests a 20% prevalence rate of carriers in the cattle population. The use of the mean parasitaemia is proposed to serve as a babesiosis clinical risk indicator. This approach could also be used in other babesia infections provided the lowest detectable parasitaemia level (threshold level) could be resolved for each parasite species.     

Progression towards endemic stability to bovine babesiosis in cattle introduced onto a game ranch

An opportunity to study progression toward endemic stability to Babesia bigemina arose when cattle were reintroduced onto a game ranch in 1999 after an absence of three years. The study was conducted between August 2000 and June 2001. The unvaccinated breeding cows were sampled only once. Calves born during October 1999 were initially vaccinated against B. bigemina and Babesia bovis at the age of 4 months and were then bled at 10, 17 and 20 months of age. Calves born during 2000 were bled at 7 and 8 months of age. Sera were collected from all the cattle sampled and later tested for antibodies against B. bigemina and B. bovis using the indirect fluorescent antibody (IFA) test. Although endemic stability to B. bigemina had not been achieved at Nooitgedacht 2 years after resumption of cattle ranching, the high seroprevalence in the unvaccinated 8-month-old calves suggested that the situation was approaching stability and that calf vaccination against bovine babesiosis was not required. Tick control should therefore be restricted to prevent excessive tick worry. Only vaccinated cattle were positive to B. bovis and it was concluded that the parasite was absent from the ranch.     

Detection of Babesia divergens in southern Norway by using an immunofluorescence antibody test in cow sera

Background

The incidence of bovine babesiosis, caused by Babesia divergens (Apicomplexa: Piroplasmida) has decreased markedly since the 1930 s, but may re-emerge as a consequence of climate change and changes in legislation and pasturing practices. This is a potentially serious disease, with both economical and animal welfare consequences. Therefore, there is a need to survey the distribution of B. divergens.

Methods

We tested sera from 306 healthy pastured cows from 24 farms along the southern Norwegian coast by using an indirect immunofluorescence IgG antibody test (IFAT). Fractions of seropositive cows were compared by calculating 95% CI.

Results

The results of this test showed that 27% of the sera were positive for B. divergens antibodies. The fraction of antibody-positive sera that we detected showed a two-humped distribution, with a high fraction of positives being found in municipalities in the western and eastern parts of the study area, while the municipalities between these areas had few or no positive serum samples.

Conclusions

Neither the farmers'' observations nor the Norwegian Dairy Herd Recording System give an adequate picture of the distribution of bovine babesiosis. Serological testing of cows by using IFAT is a convenient way of screening for the presence of B. divergens in an area.     

The impact of 2 dipping systems on endemic stability to bovine babesiosis and anaplasmosis in cattle in 4 communally grazed areas in Limpopo Province, South Africa

A 12-month study was conducted in 4 communal grazing areas in the Bushbuckridge region, Limpopo Province, South Africa. The main objective was to investigate the impact of reduced acaricide application on endemic stability to bovine babesiosis (Babesia bigemina and Babesia bovis) and anaplasmosis (Anaplasma marginale) in the local cattle population. To this end 60 cattle in each communal grazing area were bled at the beginning and the conclusion of the experimental period and their sera were assayed for B. bovis, B. bigemina and Anaplasma antibodies. Cattle in the intensively dipped group were dipped 26 times and maintained on a 14-day dipping interval throughout the study, whereas cattle in the strategically dipped group were dipped only 13 times. Three cattle, from which adult ticks were collected, were selected from each village, while immature ticks were collected by drag-sampling the surrounding vegetation. During the dipping process, a questionnaire aimed at assessing the prevalence of clinical cases of tick-borne disease, abscesses and mortalities was completed by an Animal Health Technician at each diptank. An increase in seroprevalence to B. bovis and B. bigemina and a decrease in seroprevalence to Anaplasma was detected in the strategically dipped group while in the intensively dipped group the converse was true. Amblyomma hebraeum was the most numerous tick species on the cattle, and Rhipicephalus (Boophilus) microplus was more plentiful than Rhipicephalus (Boophilus) decoloratus. Drag samples yielded more immature stages of A. hebraeum than of Rhipicephalus (Boophilus) spp. The incidence of clinical cases of tick-borne disease and of abscesses increased in the strategically dipped group at the start of the survey.     

Studies on the use of gerbil-derived Babesia divergens antigen for diagnosis of bovine babesiosis

Babesia divergens antigen obtained from bovine and gerbil erythrocytes was compared for the diagnosis of bovine babesiosis by the indirect immunofluorescence antibody test (IFAT) and the enzyme-linked immunosorbent assay (ELISA). Using a range of sera from the field and from experimental cattle, it was found that antigen from the two sources did not differ significantly in sensitivity or specificity. Antigen from gerbils may, therefore, be used for serological surveys of bovine babesiosis caused by B. divergens. The IFAT and ELISA were also compared and it was concluded that they are equally effective in the detection of positive samples. For small-scale surveys, the IFAT using gerbil-derived antigen is adequate, but for large surveys the ELISA is preferable.     

Identification of ticks and detection of blood protozoa in friesian cattle by polmerase chain reacton test and estimation of blood parameters in district Kasur,Pakistan

The study was carried out to detect Theileria annulata, the causative agent of theileriosis, and Babesia bovis, the causative agent for babesiosis, in Friesian cattle by PCR and conventional blood smear examination. One hundred blood samples obtained from diseased Friesian cattle kept on private livestock farms at Pattoki, District Kasur, Pakistan were collected in addition to 20 blood samples obtained from non-diseased animals. The disease manifestations observed clinically included high fever, swelling of sub mandibular and sub scapular lymph nodes, weakness, increased respiration and pulse, anorexia, loss of condition and rough hair coat. Neurologic sign of in coordination was also seen in weak animals. Signs of lacrimation, pale conjunctiva, diarrhoea, dyspnea and frothy nasal discharge were observed in only one animal. Clinically nine animals showed signs of haemoglobinuria. Diagnosis of bovine theileria and babesia species was based on finding many intraerythrocytic piroplasms of both blood protozoa with clinical signs associated with anaemia, lymph node hyperplasia and haemoglobinuria. One hundred samples of ticks were also collected for identification of vector. Results showed that the prevalence of Hyalomma tick was highest (15%) followed by Boophilus (12%), Haemaphysalis (5%) and Rhipicephalus (3%). The blood smear examination showed 21% (21/100) samples positive for blood parasites out of which 66.6% (14/ 21) samples were positive for theileriosis while 42.8% (9/21) were positive for babesiosis. It was also recorded that 66.66% (6/9) samples were positive for B.bigemina while 33.33% (3/9) were positive for B.bovis. The results showed that 60% (60/100) samples were positive for blood parasites by PCR test. Out of these 60% (36/60) were positive for T.annulata while 33.33% (20/60) were positive for babesia. The specificity and sensitivity of PCR test was higher than blood smear examination. The blood parameters in haemoparasites infection were also analyzed and the results showed significant decrease in total erythrocyte count and haemoglobin while MCV, MCH values increased and MCHC was slightly less than normal indicating macrocytic hypochromic anaemia.     

A Vegetation Index qualifying pasture edges is related to Ixodes ricinus density and to Babesia divergens seroprevalence in dairy cattle herds

Babesia divergens, transmitted by the tick Ixodes ricinus, is the main agent of bovine piroplasmosis in France. This Apicomplexa often is present in asymptomatic carriers; however, clinical cases are rare. While numerous factors are known to influence tick density, no risk factor of contact with B. divergens has been identified for cattle. Our study aimed to explore whether a Vegetation Index could serve as an indirect indicator of within-herd B. divergens seroprevalence. In February 2007, blood samples were taken from all of the cows in 19 dairy cattle herds in Western France and IFAT serology was performed individually to measure B. divergens seroprevalence. The following spring, I. ricinus nymphs were collected by drag sampling along transects on the vegetation of each farm's pasture perimeters. Tick density was related significantly to a Vegetation Index (V.I., ranging from 1 to 5) that took into account the abundance of trees and bushes on the edge of pastures: most ticks (57%) were found in transects with the highest V.I. (covering 15% of the explored surface in the study area). At the farm level, the proportion of transects presenting I. ricinus nymphs was significantly related to B. divergens seroprevalence: the farms with more than 15% of transects with I. ricinus had a significantly higher risk of high seroprevalence. The proportion of pasture perimeters where the V.I.=5 also was significantly related to B. divergens seroprevalence: the farms where more than 20% of transects had a V.I.=5 had a significantly higher risk of high seroprevalence. Given that the Vegetation Index is a steady indicator of the potential I. ricinus density in the biotope, we recommend that the risk of high B. divergens seroprevalence in cows be evaluated using this tool rather than drag samplings.     

First serological and molecular evidence on the endemicity of Anaplasma ovis and A. marginale in Hungary

Recurring and spontaneously curing spring haemoglobinuria was recently reported in a small sheep flock in a selenium deficient area of northern Hungary. In blood smears of two animals showing clinical signs, Anaplasma-like inclusion bodies were seen in erythrocytes. To extend the scope of the study, 156 sheep from 5 flocks and 26 cattle from 9 farms in the region were examined serologically with a competitive ELISA to detect antibodies to Anaplasma marginale, A. centrale and A. ovis. The seropositivity in sheep was 99.4%, and in cattle 80.8%. A. ovis and A. marginale were identified by PCR and sequence analysis of the major surface protein (msp) 4 gene in sheep and cattle, respectively. Haemoglobinuria, an unusual clinical sign for anaplasmosis might have been a consequence of transient intravascular haemolysis facilitated by selenium deficiency in recently infected sheep, as indicated by the reduction of mean corpuscular haemoglobin concentration (MCHC). Membrane damage was also demonstrated for parenchymal cells, since their enzymes showed pronounced elevation in the plasma. Ticks collected from animals in the affected as well as in neighbouring flocks revealed the presence of Dermacentor marginatus, Ixodes ricinus and D. reticulatus, with the dominance of the first. The present data extend the northern latitude in the geographical occurrence of ovine anaplasmosis in Europe and reveal the endemicity of A. ovis and A. marginale in Hungary.     

Clinical manifestations of canine babesiosis in Hungary (63 cases)

Clinical observations of Babesia canis infection in 63 dogs during a 1-year period are summarised, demonstrating the pathogenicity of the Babesia strain endemic in Hungary. Most patients had babesiosis in the spring and autumn, correlating with the seasonal activity of ticks. Male animals appeared in higher numbers, probably due to an overrepresentation of outdoor dogs. Uncomplicated babesiosis was diagnosed in 32 cases. The disease affected dogs of any age in this study. Symptoms were similar to those published from other parts of the world: lethargy, fever, splenomegaly, pallor, icterus, haemoglobinuria and presence of ticks were the most common observations. Thrombocytopenia, lymphopenia and neutropenia were frequent haemogram changes. Imidocarb appeared to be highly effective in eliminating the Babesia infection. Thirty-one animals demonstrated babesiosis with complications. Most Rottweilers (7/9) developed complicated disease. Old age was a risk factor for multiple complications. Multiple organ manifestations had poor prognosis. Hepatopathy (44%), pancreatitis (33%), acute renal failure (ARF; 31%) and disseminated intravascular coagulation (DIC; 24%) were frequent complications, while immune-mediated haemolytic anaemia (IMHA; 10%), acute respiratory distress syndrome (ARDS; 6%) and cerebral babesiosis (3%) were rarely observed. There was a significant difference between the mean age of dogs having uncomplicated disease, babesiosis with a single complication and babesiosis with multiple complications (3.4, 4.8 and 8.6 years, respectively, p < 0.001). The recovery rate (78, 68 and 25%, respectively, p = 0.005) and mortality rate (3, 21 and 67%, respectively, p < 0.001) also tended to differ significantly in these groups. Systemic inflammatory response syndrome (SIRS) and DIC are two possible pathways leading to multiple organ dysfunction syndrome (MODS) in babesiosis. DIC was found to predict MODS more sensitively in this study than SIRS: there were 6 animals developing MODS out of 11 identified with DIC, while only 5 dogs developed MODS out of 22 having SIRS.     

Autochthonous cases of canine babesiosis in the canton Solothurn

Starting in November 2003 a series of five clinical cases of canine babesiosis was registered in the region of Oberg?sgen (canton Solothurn). All presented dogs showed increased body temperature, thrombocytopenia and hemoglobinuria, and none of the dogs had been abroad or visited endemic regions in the southern or western part of Switzerland so far. Babesia canis was detected in the blood smears of all five patients, but only three had detectable specific antibodies against this parasite. However, seroconversion was found in a second sample collected from the negative dogs at a later timepoint, confirming the diagnosis of canine babesiosis. The blood samples of two parasitized dogs were used for DNA-isolation and were tested with a Babesia-specific PCR, detecting the 18S rRNA-gene. Sequencing of the amplified products revealed a 100% identity with the sub-species B. canis canis. The ticks Rhipicephalus sanguineus and Dermacentor marginatus are potential vectors for B. canis. In the area where the infection with B. canis was suspected a total of 152 ticks was collected and characterized; one was a female R. sanguineus.Although babesia could not be detected in the latter tick and the final prooffor the complete life cycle is still lacking, it is very probable that B. canis has become autochthonous in the canton Solothurn.     

West-to-east differences of Babesia canis canis prevalence in Dermacentor reticulatus ticks in Slovakia

Babesia canis canis is the most frequent causative agent of canine babesiosis in Central Europe, frequently causing severe disease. Recently, many new endemic foci of this disease have been reported from European countries. Growing incidence of canine babesiosis was recorded also in Slovakia during the last decade, from first cases in eastern Slovakia ten years ago to recent cases all over the south of the country. We have used nested PCR-RFLP method to study prevalence of B. c. canis in its natural tick vector Dermacentor reticulatus, collected at three geographically isolated lowland areas of southern Slovakia situated in the southeast, southwest, and west of Slovakia, respectively. The highest prevalence of B. c. canis was observed in D. reticulatus from eastern Slovakia (14.7%; n=327), whereas the prevalence in southwest was significantly lower (2.3%; n=1205). Notably, all 874 D. reticulatus ticks collected at Záhorská ní?ina lowland (W Slovakia) were B. c. canis-negative. Recorded differences in Babesia prevalence concurs well with the shift in incidence of clinical cases of canine babesiosis as observed by vet practitioners. Presented results revealed that eastern Slovakia represents an area of high risk of B. c. canis infection, whereas western areas of the country still remain Babesia canis-free.     

Application of PCR assays to determine the genotype of Babesia bovis parasites isolated from cattle with clinical babesiosis soon after vaccination against tick fever

OBJECTIVE: To demonstrate the value of PCR assays to determine the genotypes of Babesia bovis in cattle with clinical signs of babesiosis within 3 weeks after vaccination against tick fever. DESIGN: Samples from 5 cases of babesiosis in cattle soon after vaccination against tick fever were analysed in two PCR assays. PROCEDURE: Parasite DNA was purified from blood taken from cattle with signs of babesiosis within 3 weeks of vaccination against tick fever. DNA was also prepared from the tissues of animals that died of babesiosis. Two PCR assays that amplify repeat sequences of DNA within the B bovis genes, Bv80 and BvVA1, were used to differentiate the genotypes of field isolates and vaccine strains of B bovis. RESULTS: One of the five cases of babesiosis was found to be caused by a vaccine strain, but PCR analyses showed that the predominant isolate in the other four cases was not the vaccine strain. CONCLUSIONS: PCR assays on the DNA of B bovis obtained from the blood or tissues of cattle clinically affected with tick fever within 3 weeks after vaccination are useful to distinguish between vaccine strains and field isolates as the source of infection.     

Attainment of endemic stability to Babesia bigemina in cattle on a South African ranch where non-intensive tick control was applied

The seroprevalence of Babesia bigemina and Babesia bovis antibodies in non-vaccinated cattle was monitored on a South African ranch. The main objective was to assess the endemic stability to bovine babesiosis in cattle maintained under relaxed tick-control measures. Cattle were bled at the age of 7, 8, 10, 17, 20 and 30-120 months and the sera tested for the presence of antibodies using the indirect fluorescent antibody (IFA) test. None of the animals were positive to B. bovis. Seroprevalence of B. bigemina antibodies was 46, 70, 90, 92, 54 and 82% in the various age classes, respectively. Endemic stability was therefore reached by the time the calves were 9 months old. The high seroprevalence of B. bigemina was probably due to the high vector tick population on the ranch, which would have encouraged frequent transmission of B. bigemina. An endemically stable situation to B. bigemina could therefore be achieved merely by adopting a tick-control method that allows a reasonable number of ticks on cattle rather than relying entirely on intensive tick control and vaccination.     

Effect of breed of cattle on transmission rate and innate resistance to infection with Babesia bovis and B bigemina transmitted by Boophilus microplus

OBJECTIVE: To assess the effect of breed of cattle on the transmission rates of and innate resistance to Babesia bovis and B bigemina parasites transmitted by Boophilus microplus ticks. DESIGN: Groups of 56 purebred B indicus and 52 B indicus cross B taurus (50%, F1 generation) steers were placed in a paddock seeded with and also naturally infested with B microplus which were the progeny of females ticks fed on B taurus cattle specifically infected with a virulent isolate of B bovis. The cattle were placed in the infested paddock 50 days after seeding had started. PROCEDURE: Cattle were inspected from horseback daily for 50 days. Clinically ill cattle were brought to yards and assessed by monitoring fever, depression of packed-cell volume, parasitaemia and severity of clinical signs. Any animals that met preset criteria were treated for babesiosis. Blood samples were collected from all cattle on day 28, 35 and 42 after exposure and antibodies to Babesia spp and packed cell volume measured. RESULTS: All steers, except for one crossbred, seroconverted to B bovis and B bigemina by day 35 and 75% of the crossbred steers showed a maximum depression in packed cell volume of more than 15% due to infection with Babesia spp compared with only 36% of the B indicus group. Ten of the 52 crossbreds and 1 of the 56 B indicus steers showed severe clinical signs. Two of the crossbreds required treatment of which one died 2 weeks after initial treatment. CONCLUSIONS: Pure-bred B indicus cattle have a high degree of resistance to babesiosis, but crossbred cattle are sufficiently susceptible to warrant the use of preventive measures such as vaccination. Transmission rates of B bovis and B bigemina to B indicus and crossbred cattle previously unexposed to B microplus were the same.     

Babesia canis canis in dogs from Hungary: detection by PCR and sequencing

Canine babesiosis in Hungary has always been a severe and frequent disease, attributed to infection with Babesia canis transmitted by Dermacentor reticulatus. Identification of the disease agent has been based merely on size and morphology of the intraerythrocytic parasites and no evidence has been found concerning the subspecies (genotype) of B. canis. Therefore, a molecular survey on natural Babesia infection of dogs in Hungary using PCR and sequence analysis was attempted to clarify the subspecies (genotype) and to obtain information on the occurrence of B. canis. A total of 44 blood samples from dogs showing clinical signs of babesiosis were collected. A piroplasm-specific PCR amplifying the partial 18S rRNA gene yielded an approximately 450 bp PCR product in 39 (88.6%) samples. Thirteen positive samples originated from Budapest and 26 from 21 other locations. Five PCR products were chosen randomly for sequencing. The partial 18S rDNA sequences were submitted to GenBank (accession numbers AY611729; AY611730; AY611731; AY611732 and AY611733). The sequences showed 100% homology to one another or differed by one nucleotide. BLAST search against GenBank revealed the highest similarity (99.8 or 100%) with Babesia canis canis. The implication of these data, for the further study and diagnosis of canine babesiosis is discussed.