Is the detection of anti-Rhipicephalus sanguineus (Rs24p) antibodies a valuable epidemiological tool of tick infestation in dogs?

Antibodies against the 24 kDa Rhipicephalus sanguineus (Rs24p) protein were detected by ELISA to evaluate the relationship between antibodies and tick infestation. The mean titer of 3 dogs that underwent 2 experimental infestations with adult ticks was transiently increased after the second infestation. There was a significant difference in mean titers between positive control dogs naturally infested with ticks and tick-naive dogs. These results suggested that anti-Rs24p antibodies detected by ELISA are a marker of tick exposure. There was no significant difference in mean titers between tick-naive dogs and seropositive dogs to Ehrlichia canis. Some dogs positive for E. canis antibodies showed, however, higher titers than most tick-naive dogs. R. sanguineus may be related to the E. canis infection in Japan.     

Prevalence of Babesia canis, Borrelia afzelii, and Anaplasma phagocytophilum infection in hard ticks removed from dogs in Warsaw (central Poland)

The purposes of this study were to specify the occurrence and prevalence of Babesia canis, Borrelia burgdorferi sensu lato, and Anaplasma phagocytophilum in ticks removed from dogs in Warsaw, and to determine the Borrelia species occurring in Ixodes ricinus ticks. Among 590 collected ticks, 209 were identified as I. ricinus, and 381 as Dermacentor reticulatus. DNA of B. canis was detected in 11% of D. reticulatus ticks. We found that 6.2% of I. ricinus ticks harbored B. burgdorferi s.l. specific DNA and 2.9% harbored A. phagocytophilum DNA. In these samples sequencing of the detected Borrelia amplicon confirmed infection with Borrelia afzelii genospecies. New sequences were submitted to the GenBank database (accession no. EU152128, EU152127, EU152126). This work is the first detection of B. afzelii and A. phagocytophilum in ticks from Warsaw, and the first survey for the prevalence of B. canis, B. afzelii, and A. phagocytophilum in ticks in central Poland.     

Anaplasma phagocytophilum in dogs in Germany

A total number of 111 dogs were included in the present prospective study investigating the prevalence of Anaplasma phagocytophilum in dogs in Germany. Dogs were divided into two groups. Dogs of group 1 (n = 49) showed clinical and/or haematological signs seen in infections with A. phagocytophilum, whereas those of group 2 (n = 62) did not have any evidence of anaplasmosis. For each dog, an A. phagocytophilum 16S rRNA-nested polymerase chain reaction (PCR) of ethylenediaminetetraacetic acid (EDTA)-anticoagulated whole blood analysis, a microscopic evaluation of a buffy coat and a serum indirect fluorescent antibody test (IFAT) were performed. Forty-eight seroreactive dogs were identified altogether, which amounts to an overall point prevalence of 43.2%. There was no significant difference between the seroreactivity to A. phagocytophilum antigens among group 1 (44.9%) and 2 (41.9%) (P > 0.5). Seven dogs (6.3%) had positive PCR results. All of them were seroreactive. Six belonged to group 1. Morulae in neutrophilic granulocytes were found in two dogs of group 1 but in none of group 2. Both dogs were seroreactive. Very high antibody titres (> or =1:1024) were detected significantly more frequently in dogs with clinical signs attributable to infection with A. phagocytophilum (group 1) than in those without (group 2) (P < 0.001). There was no significant correlation of overall positives or antibody titres to age, breed, sex, or whether the dogs were family or working dogs. Dogs with high tick infestation were significantly more often seroreactive to A. phagocytophilum than those with no or low tick infestation (P = 0.007). In conclusion, there seems to be a high risk of infection with A. phagocytophilum in Germany. Results of this study suggest that severe illness solely caused by A. phagocytophilum may be possible although definitive evidence does not exist. Very high antibody titres (>1:1024) may be associated with clinical anaplasmosis.     

Seroprevalence of Ehrlichia canis, Ehrlichia equi, and Ehrlichia risticii in sick dogs from North Carolina and Virginia

Ehrlichia canis, E. equi, and E. risticii seroprevalence was determined by microimmunofluorescent antibody testing (IFA) in a sequential population of 1,845 sick dogs admitted during a 1-year period to the North Carolina State University Veterinary Teaching Hospital. A seroreactor was defined by a reciprocal IFA titer of > or =80 to E. canis, E. equi, or E. risticii antigens. Of the 48 IFA seroreactors, 44 dogs were seroreactive to E. canis, 21 to E. equi, and 0 to E. risticii. Seventeen dogs reacted to both E. canis and E. equi antigens. There was concordance of E. canis IFA and western immunoblot (WI) test results for 36/44 dogs. Because of cross-reactivity of E. canis sera with E. equi antigens, WI was of less utility to confirm E. equi exposure. After elimination of E. canis seroreactors, there was concordance of 2/4 E. equi IFA and WI test results. Based upon a retrospective review of medical records, ehrlichiosis was diagnosed in 10/48 (21%) IFA seroreactive dogs, 9 of which were confirmed positive by WI. Of the remaining 38 IFA seroreactors, 29 also were confirmed by E. canis or E. equi WI. These results indicate that (1) ehrlichiosis was not diagnosed in the majority of serologically confirmed cases, (2) based upon E. canis and E. equi WI analysis, IFA testing was not specific (21% false positive), (3) E. canis sera cross-react with E. equi antigens, and (4) serologic evidence of E. risticii infection was lacking in the dog population studied.     

Use of imidacloprid-permethrin to prevent transmission of Anaplasma phagocytophilum from naturally infected Ixodes scapularis ticks to dogs

One group of eight beagles was treated with a combination of imidacloprid and permethrin 7 days before exposure to Ixodes scapularis ticks that were naturally infected with Anaplasma phagocytophilum. A second group of eight beagles was not treated and was also exposed to infected ticks. Seven of eight non-treated dogs--but none of the treated dogs--developed specific antibodies to A. phagocytophilum. Results of this study indicate that a combination of imidacloprid and permethrin can prevent transmission of A. phagocytophilum to dogs if administered before exposure to infected ticks.     

Comparison of results for serologic testing and a polymerase chain reaction assay to determine the prevalence of stray dogs in eastern Tennessee seropositive to Ehrlichia canis

OBJECTIVE: To determine the prevalence of stray dogs in eastern Tennessee seropositive to Ehrlichia canis and examine the correlation between results for an ELISA, indirect immunofluorescent antibody (IFA) test, and polymerase chain reaction (PCR) assay. SAMPLE POPULATION: Blood samples obtained from 90 adult dogs admitted to an animal shelter in eastern Tennessee. PROCEDURE: Serum samples were analyzed for antibodies against E. canis by use of a commercially available ELISA kit, 2 IFA tests, and a PCR assay; testing was performed at the University of Tennessee (TN) and North Carolina State University (NCSU). The PCR amplification was performed by use of DNA extracted from EDTA-anticoagulated blood and primers designed to amplify DNA of Ehrlichia spp. RESULTS: Antibodies against E. canis were detected in only 1 dog by use of the ELISA. By IFA testing at TN, 10 of 90 (11%) dogs were seroreactive against E. canis antigens, all of which had medium to high titers to E. canis. Only 5 of the 10 TN seroreactors were also reactive against E. canis antigens in IFA tests conducted at NCSU, and all 5 had low to medium titers. The DNA of Ehrlichia spp was not amplified in any blood samples by use of PCR assays conducted at the TN or NCSU. CONCLUSIONS AND CLINICAL RELEVANCE: The discordant ELISA, IFA, and PCR results obtained in this study were unexpected and may have been related to exposure of dogs to an Ehrlichia species other than E. canis, such as E. ewingii.     

Antibodies reactive with Ehrlichia canis, Ehrlichia phagocytophila genogroup antigens and the spotted fever group rickettsial antigens, in free-ranging jackals (Canis aureus syriacus) from Israel.

A seroepidemiological survey was conducted to investigate the prevalence of antibodies reactive with the Ehrlichia canis and Ehrlichia phagocytophila genogroup antigens, and the spotted fever group (SFG) rickettsiae antigens in jackals in Israel (Canis aureus syriacus), to assess the possible role of the jackal in the epidemiology of these diseases. Fifty-three serum samples from jackals were assayed by the indirect immunofluorescence antibody test. Antibodies to E. canis were detected in 35.8% serum samples while 26.4% of the samples tested were positive to Ehrlichia chaffeensis. Twenty-six percent of the jackals tested were seropositive to E. phagocytophila, of which 5.7% were seropositive to E. phagocytophila alone without any seroreactivity to either E. canis or E. chaffeensis. Fifty-five percent of the jackals were seropositive to the SFG-rickettsiae antigens. The results suggest a high exposure rate of jackals in Israel to E. canis. Positive reactivity to E. chaffeensis was considered to be due to antigenic cross-reactions with E. canis. The study demonstrated for the first time the presence of E. phagocytophila antibodies in free-range jackals. The high incidence of antibodies to the SFG-rickettsiae and their relatively high antibody titers was suggestive of either recent or persistent infection. The possibility that jackals may play a role in the transmission of E. canis, E. phagocytophila and the SFG-rickettsiae for human and canine infections is discussed.     

A serosurvey of Hepatozoon canis and Ehrlichia canis antibodies in wild red foxes (Vulpes vulpes) from Israel

A seroepidemiological survey was conducted to investigate the prevalence of antibodies reactive with Ehrlichia canis and Hepatozoon canis antigens in free-ranging red foxes (Vulpes vulpes) in Israel. Of 84 fox sera assayed, 36% were seropositive for E. canis by the indirect fluorescent antibody (IFA) test and 24% were positive for H. canis using an enzyme-linked immunosrbent assay (ELISA). Canine ehrlichiosis and hepatozoonosis appear to be endemic in the wild red fox populations in Israel, and foxes may serve as a reservoir for infection of domestic dogs and other wild canine species.     

Epidemiological survey of Anaplasma platys and Ehrlichia canis using ticks collected from dogs in Japan

Detection of Anaplasma platys and Ehrlichia canis in ticks recovered from dogs in Japan was attempted using a species-specific nested PCR based on the 16S rRNA gene. A total of 1211 ticks recovered from 1211 dogs from all over Japan were examined for A. platys and E. canis. Four tick samples from Fukushima, Miyazaki and Kagoshima Prefectures recovered from four different dogs showed a positive reaction for A. platys. Although the four dogs did not show any clinical signs and no blood examination data were available, it is possible that A. platys has already been spread widely in Japan. No positive reactions were observed in any ticks examined for E. canis.     

Ehrlichial infection in Cameroonian canines by Ehrlichia canis and Ehrlichia ewingii

Ehrlichia chaffeensis and Ehrlichia ewingii are agents of emerging human ehrlichioses in North America and are transmitted primarily by Amblyomma americanum ticks, while Ehrlichia canis is the globally distributed cause of canine monocytic ehrlichiosis (CME) and is transmitted by the brown dog tick, Rhipicephalus sanguineus. Although E. canis and Ehrlichia ruminantium are endemic in Africa, the presence of ehrlichial agents in dogs and ticks in Cameroon has not been investigated. The objective of this study was to determine the prevalence of ehrlichial infections in Cameronian dogs using a combination of serologic and molecular methods. Peripheral blood was collected, clinical signs and the presence or absence of ticks on dogs (n=104) presenting for various reasons at local veterinary clinics around the Mount Cameroon region were noted. IFA identified 33 dogs (32%) with antibodies reactive with E. canis, and reactivity of these sera with all major E. canis antigens (200, 140, 95, 75, 47, 36, 28, and 19-kDa) was confirmed by immunoblotting. Multicolor real-time PCR detected ehrlichial DNA (E. canis (15) and E. ewingii (2)) in 17 dogs (16.3%), all of which had attached ticks at time of presentation. The dsb amplicons (378 bp) from E. canis and E. ewingii were identical to gene sequences from North American isolates. This study identifies canine ehrlichiosis as a prevalent unrecognized cause of disease in Cameroonian canines.     

Molecular evidence of vector-borne pathogens coinfecting dogs from Poland

Ticks of the genus Ixodes are vectors for many pathogens, including Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum and Rickettsia spp., and may also serve as vectors for Bartonella spp. However, the role of ticks in Bartonella transmission requires additional studies. The aim of this study was to investigate whether coinfection with two or more vector-borne pathogens can occur in the following three groups of dogs: I - dogs with suspected borreliosis (N = 92), II - dogs considered healthy (N = 100), and III - dogs with diagnosed babesiosis (N = 50). Polymerase chain reactions were performed to detect DNA of Anaplasma phagocytophilum, Rickettsia spp. and Bartonella spp. in the blood of dogs. In dogs of Group I, the DNA of both A. phagocytophilum and Bartonella sp. was detected (14% and 1%, respectively). In eight dogs, coinfection was indicated: A. phagocytophilum or Bartonella sp. with B. burgdorferi s.l. (the presence of antibodies against and/or DNA B. burgdorferi s.l.). In the case of five dogs positive for A. phagocytophilum DNA, no coinfection with B. burgdorferi s.l. was shown. In Group II, the DNA of A. phagocytophilum was detected in four dogs. In Group III, no pathogenic agents possibly transmitted by ticks were confirmed. No DNA of R. helvetica was detected in any of the groups studied.     

Serologic diagnosis of infectious cyclic thrombocytopenia in dogs using an indirect fluorescent antibody test

An indirect fluorescent antibody test was used for detection of serum antibodies to the platelet-specific rickettsial organism that is the causative agent of infectious cyclic thrombocytopenia (ICT) in dogs. The test converted from negative to positive in 7 of 7 experimentally inoculated dogs. One of 2 attempts to recover the rickettsial agent of ICT from naturally occurring seropositive dogs, by blood inoculation of experimental dogs, was successful. Seemingly, the test did not detect antibodies to Ehrlichia canis, nor did a similar test, using E canis antigen slides, detect antibodies to the rickettsial agent of ICT. The rickettsial agent of ICT has been classified tentatively as E platys. When applied to sera from a group of healthy random-source dogs, the test revealed a relatively low (5%) occurrence of positive reactions. A higher occurrence of positive reactions (35%) was noticed in sera from a group of thrombocytopenic dogs from the University of Florida. A majority of these positive sera were also positive for antibodies to E canis. The highest occurrence of positive reactions was found (greater than 50%) in E canis-positive sera from dogs at the University of Florida, as well as from dogs from 9 other states.     

Transstadial and intrastadial experimental transmission of Ehrlichia canis by male Rhipicephalus sanguineus

The acquisition and transmission of rickettsial pathogens by different tick developmental stages has important epidemiological implications. The purpose of this study was to determine if male Rhipicephalus sanguineus can experimentally acquire and transmit Ehrlichia canis in the absence of female ticks. Two trials were performed where nymphal and male R. sanguineus were simultaneously acquisition fed on the same infected donor hosts, and transstadially or intrastadially exposed male ticks were fed on separate pathogen-free dogs as a test for transmission. A single-step p30-based PCR assay was used to test canine and tick hosts for E. canis infections before and after tick feeding. E. canis was detected after either intrastadial or transstadial passage in male ticks, the organism remained detectable in both tick groups after transmission feeding, and both tick groups transmitted the rickettsia to susceptible dogs. Infection of dogs via tick feeding resulted in milder clinical signs and lower antibody titers than intravenous inoculation of carrier blood, but further investigation is needed to understand the mechanisms responsible for this observation. These results demonstrate that male R. sanguineus can take multiple feedings, and that they can both acquire and transmit E. canis in the absence of female ticks. This tick development stage could be important in transmission of E. canis, and perhaps related pathogens, between vertebrate hosts under natural and experimental conditions.     

Typical and atypical manifestations of Anaplasma phagocytophilum infection in dogs

Eighteen clinically ill dogs, naturally infected with Anaplasma phagocytophilum, were examined at a veterinary practice in Baxter, Minnesota. A clinical examination, complete blood cell count, enzyme- linked immunosorbent assay (ELISA) for A phagocytophilum, Borrelia burgdorferi, and Ehrlichia canis antibodies and Dirofilaria immitis antigen, and a polymerase chain reaction test for A phagocytophilum DNA were obtained for all dogs. Physical examination findings included fever, arthropathy, lymphadenopathy, epistaxis, acute gastritis, cervical hyperpathia, and central nervous system dysfunction. Complete blood cell count abnormalities included thrombocytopenia, morulae in neutrophils, anemia, leukopenia, eosinopenia, lymphopenia, and monocytosis. Seroreactivity to A phagocytophilum was found in 61%, B burgdorferi antibodies in 17%, and D immitis antigen in 5% of the dogs. Fever, arthropathy, neurologic dysfunction, and epistaxis are clinical syndromes that can be associated with A phagocytophilum infection. Treatment with doxycycline resulted in rapid resolution of clinical signs in all dogs.     

Bartonella henselae IgG antibodies are prevalent in dogs from southeastern USA

In contrast to the large body of literature regarding Bartonella henselae in humans and cats, there is little information about B. henselae as an infectious agent in dogs. Due to the paucity of information regarding the B. henselae serology in dogs, we performed a cross-sectional serosurvey using B. henselae antigen in order to compare the seroprevalence between sick and healthy dogs from the south-eastern USA. Ninety-nine sera were collected from clinically healthy dogs. Three hundred and one sera from sick dogs were submitted to North Carolina State University for serologic screening against a panel of arthropod-transmitted organisms. Serological tests were performed using B. henselae (Bh), Rickettsia rickettsii (Rr), Ehrlichia canis (Ec), Bartonella vinsonii subspecies berkhoffii (Bvb), Babesia canis (Bc) and Borrelia burgdorferi (Bb) antigens. Serum B. henselae IgG antibodies were detected in 10.1% of healthy dogs and in 27.2% of sick dogs. The difference in seroprevalence between the two groups was statistically significant. The majority of seroreactive dogs (80%) had low titers of 1:64 or 1:128. In healthy dogs, seroprevalence for Rr was 14.1% and for Bvb was 1%. In sick dogs, Rr seroprevalence was 29.7%, Ec 6.5%, Bvb 4.7%, Bb 1.7% and Bc was 0.85%. Of the sick dogs that were seroreactive to B. henselae antigens, 40.6% were also seroreactive to Rr, 15.0% reactive to Bvb antigens, 14.8% reactive to Ec antigens, 1.8% reactive to Bc antigens and 1.75% reactive to Bb antigens. Sera from dogs experimentally infected with B. vinsonii subsp. berkhoffii, E. canis or R. rickettsii did not cross react with B. henselae antigens, by IFA testing. This study indicates that B. henselae IgG antibodies are prevalent in healthy and sick dogs living in the south-eastern USA. Nevertheless, further studies are needed to evaluate the epidemiological, clinical and zoonotic relevance of B. henselae infection in dogs.     

The low seroprevalence of tick-transmitted agents of disease in dogs from southern Ontario and Quebec

Infectious diseases caused by pathogens transmitted by ticks and other insect vectors are an important cause of morbidity and mortality in both dogs and humans throughout North America. The purpose of this study was to determine the seroprevalence of selected vector-transmitted pathogens in southern Ontario and Quebec. Samples submitted to the Vector Borne Disease Diagnostic Laboratory (VBDDL) at the North Carolina State University College of Veterinary Medicine were evaluated for antibodies to Ehrlichia canis, Anaplasma phagocytophilum, Babesia canis, Bartonella henselae, Borrelia burgdorferi, Bartonella vinsonii subspecies berkhoffii, and Rickettsia rickettsii. Information regarding breed and the city or province from which the sample originated was recorded; however, travel history was unknown for the majority of dogs. Overall seroprevalence to these tick-borne pathogens in southern Ontario and Quebec is low compared with most regions of the United States, suggesting that veterinarians in this region of Canada should pursue diagnostic evidence of infection in dogs with a travel history or prior residence in areas endemic for exposure to tick-borne infections.     

Serological survey for antibodies reactive with Ehrlichia canis and E. chaffeensis in dogs from the Bloemfontein area, South Africa

Sera from 161 dogs in the Bloemfontein area in South Africa were tested for the presence of antibodies reactive with Ehrlichia canis and E. chaffeensis by indirect fluorescent antibody testing. Overall, 68 (42%) of the dogs had significant antibody titres (> or = 1/64) against E. canis and 61 (38%) had significant titres (> or = 1/64) against E. chaffeensis. Seven (11%) dogs had higher titres to E. chaffeensis than E. canis (1/2048 and 1/1024 (2 dogs); 1/1024 and 1/512 (2 dogs); 1/2048 and 1/512; 1/512 and 1/256 and 1/512 and < 1/64, respectively). The remaining seropositive dogs had equal (n = 26; 42%) or 2-(n = 17; 25%), 3-(n = 13; 2%) or 4-fold (n = 5; 7%) higher titres against E. canis. Dogs from economically depressed, high-density suburbs (60/112; 48%) had significantly higher prevalences of antibodies against E. canis than those from more affluent, low-density suburbs (8/49; 14%) (chi 2 = 19.38, p < 0.001). Higher titres to E. chaffeensis than E. canis were found in dogs from affluent, low-density suburbs (3/49) and in dogs from economically depressed, high-density suburbs (4/112).     

Prevalence of Ehrlichia canis infection in thrombocytopenic dogs from Rio de Janeiro, Brazil

BACKGROUND: Infection with Ehrlichia canis causes a highly variable, multisystemic disease in dogs. Nevertheless, many clinicians in Rio de Janeiro, Brazil, use the presence of only thrombocytopenia to make a presumptive diagnosis of E canis infection. OBJECTIVE: The objective of this study was to determine the prevalence of E canis in thrombocytopenic dogs from Rio de Janeiro, Brazil, using polymerase chain reaction (PCR). METHODS: Following DNA extraction of whole blood samples from 226 dogs, PCR assays were done using primers for rickettsial DNA (including Ehrlichia spp, Anaplasma platys and A phagocytophilum) and using E canis-specific primers (16S rRNA gene). Dogs were grouped as thrombocytopenic and nonthrombocytopenic based on platelet counts. The null hypothesis that there was no difference in the prevalence of E canis in these groups was rejected at P<.05. RESULTS: Thirty-six (32.1%) of the thrombocytopenic dogs and 4 (3.5%) of the nonthrombocytopenic dogs were positive for rickettsial gene sequences (P<.0001). Further, 30 (26.8%) of thrombocytopenic dogs and 4 (3.5%) nonthrombocytopenic dogs were positive for E canis-specific gene sequences (P<.0001). CONCLUSIONS: Although the prevalence of E canis infection was higher in thrombocytopenic dogs, less than one third of these dogs had demonstrable E canis infection. Thus, thrombocytopenia is not specific for the detection of E canis infection and should not be used solely to establish a diagnosis of canine ehrlichiosis, even in a geographic area with relatively high disease prevalence.     

Evaluation of a polyvalent enzyme-linked immunosorbent assay incorporating a recombinant p44 antigen for diagnosis of granulocytic ehrlichiosis in dogs and horses

OBJECTIVE: To develop and evaluate a polyvalent ELISA incorporating a highly specific recombinant antigen (p44) for diagnosis of granulocytic ehrlichiosis in dogs and horses. ANIMALS: 32 dogs and 43 horses. PROCEDURE: Results of the ELISA were compared with results of indirect fluorescent antibody (IFA) staining and western immunoblotting incorporating whole-cell antigen. RESULTS: For the canine and equine samples, percentages of samples with positive IFA staining, western immunoblotting, and ELISA results were similar. For 29 (91 %) canine samples and 30 (70%) equine samples, results of IFA staining, western immunoblotting, and the ELISA were in complete agreement. Results of the ELISA for 3 canine serum samples known to contain antibodies to Ehrlichia canis and 12 equine serum samples known to contain antibodies to E risticii were negative. CONCLUSIONS AND CLINICAL RELEVANCE: Results of the present study suggest that a polyvalent ELISA incorporating a recombinant p44 antigen is suitable for detecting antibodies to E equi in dogs and horses.     

Sero-prevalence and risk indicators for canine ehrlichiosis in three rural areas of Brazil

Ehrlichia canis has a worldwide geographic distribution, occurring particularly in tropical and subtropical areas. In Brazil, the main vector in urban areas is believed to be the brown dog tick Rhipicephalus sanguineus, but little is known about the occurrence, transmission and other epidemiological aspects of canine ehrlichiosis in rural areas, where Amblyomma ticks are found more frequently than R. sanguineus. A sero-prevalence study of canine ehrlichiosis was carried out in three distinct rural regions of the State of Minas Gerais, Brazil. Serum samples were collected from 226 dogs living on farms in Lavras (n=85), Belo Horizonte (n=45), and Nanuque (n=96) and were analyzed by an indirect fluorescent antibody test for the detection of anti-Ehrlichia canis antibodies. Age, breed, sex, presence of ticks and packed cell volume were also recorded. There were 65.6% positive dogs in Nanuque, 37.8% in Belo Horizonte, and 24.7% in Lavras. Animals living in Nanuque were 4.6 times more likely to be serologically positive than dogs living in the other two regions and antibody titres were considerable higher in this area. Male dogs, dogs >5 years of age, those infested with ticks, and mongrels all showed higher rates of positivity. The results point to the importance of canine ehrlichiosis in rural areas and indicate the need for further studies on natural transmission and maintenance of the disease.