Prevalence and geographic distribution of Dirofilaria immitis, Borrelia burgdorferi, Ehrlichia canis, and Anaplasma phagocytophilum in dogs in the United States: results of a national clinic-based serologic survey.

We evaluated a comprehensive national database that documents canine infection with, or exposure to, four vector-borne disease agents, Dirofilaria immitis, Borrelia burgdorferi, Ehrlichia canis, and Anaplasma phagocytophilum in order to assess geographic trends in rates of positive tests. While the percent positive test results varied by agent in different regions of the United States, with D. immitis antigen and antibodies to E. canis more commonly identified in dogs from the South (3.9% and 1.3%, respectively), and antibody to B. burgdorferi and A. phagocytophilum found more frequently in dogs from the upper Midwest and Northeast (4.0-6.7% and 5.5-11.6%, respectively), evidence of at least one agent was found in dogs from every state considered. Furthermore, each organism also appeared to occur in endemic foci within larger areas of relatively low prevalence. Relocation of infected or previously exposed dogs from endemic regions likely accounts for some of the unexpected geographic distribution seen, although local transmission in previously under-recognized areas of endemicity could also be occurring. Although data were only available from the 48 contiguous states (Alaska and Hawaii were not included), taken together, our results suggest that these disease agents may be present over a wider geographic area, and thus pose greater animal and public health risks, than is currently recognized. Dogs can serve as sentinels to identify the presence of vector-borne disease agents of both veterinary and public health significance.

Occurrence of Dirofilaria immitis and tick-borne infections caused by Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato and Ehrlichia canis in domestic dogs in France: results of a countrywide serologic survey.

The occurrence of Dirofilaria immitis antigen and antibodies against tick-borne pathogens in French dogs has been analysed based on 1,050 blood samples. Serum samples of 919 dogs (group A) were sent for a variety of diagnostic investigations, further 131 dogs (group B) were tested for a tentative diagnosis of heartworm disease. All samples were tested for D. immitis antigen. Samples in group A were also tested for specific antibodies against three tick-borne pathogens (Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato and Ehrlichia canis). Results were plotted in geographical maps. Occurrence of D. immitis antigen in group A (0.22%; 95 % CI: 0.03-0.78%) was significantly lower (p < 0.0001) than in group B (6.87%; 95% CI: 3.19-12.64%). Heartworm infections in both groups were regionally restricted to the areas of Bouches-du-Rhône in the South of France and Corsica. In group A, the calculated seroprevalence was 2.72% (95% CI: 1.77-3.99%) for A. phagocytophilum, 1.09% (95% CI: 0.52-1.99%) for B. burgdorferi and 0.33% (95% CI: 0.07-0.95%) for E. canis with a distribution of the positive cases throughout the country. This study represents the first data of A. phagocytophilum seroprevalence in the French dog population.

Current surveys on the prevalence and distribution of Dirofilaria spp. in dogs in Germany.

The Central Upper-Rhine (Baden-Württemberg, Germany) is one of the warmest regions in Germany and also harbours abundant numbers of mosquitoes. Case reports on presumably autochthonous occurrence of Dirofilaria spp. were reported previously and were a reason for a further investigation into the occurrence of vector-borne pathogens. For this purpose, 44 hunting dogs from the Central Upper-Rhine region were tested between 4(th) and 29(th) June 2007. The blood samples were tested using the Knott's test and IDEXX SNAP 4Dx test. The Knott's test revealed unsheathed microfilaria identified as Dirofilaria repens by PCR in 3 dogs with no history of travelling (6.8%; 95% CI: 2.4-18.2%). The seroprevalence for Anaplasma phagocytophilum was 43.2% (95% CI: 29.7-57.8%), but only 4.5% (95% CI: 1.3-15.1%) for antibodies to Borrelia C6 peptide. Dirofilaria immitis antigen was not detected in any of the samples. A further 288 blood samples from non-hunting companion dogs of the Central Upper-Rhine region were tested negative for heartworm antigen between February and August 2007.

Clinical relevance of annual screening using a commercial enzyme-linked immunosorbent assay (SNAP 3Dx) for canine ehrlichiosis.

Eighty-six dogs were selected based upon Ehrlichia (E.) canis SNAP 3Dx positive results to determine clinical relevance of annual E. canis screening. Immunofluorescence assay showed 72 (84%) of 86 dogs were seroreactive for E. canis. Polymerase chain reaction (PCR) revealed that 12 (14%) of 86 dogs had Ehrlichia deoxyribonucleic acid; seven had E. canis, four had E. ewingii, and one was coinfected with E. chaffeensis and E. ewingii. Thrombocytopenia (<164,000 platelets/microL) was found in 28 (39%) of 72 dogs. In this study, thrombocytopenia was frequently detected in healthy Ehrlichia SNAP 3Dx-positive dogs, whereas active infection was infrequently confirmed by PCR. Therefore, treatment based upon screening results alone is not recommended.

Incidence of positive heartworm antibody and antigen tests at IDEXX Laboratories: trends and potential impact on feline heartworm awareness and prevention.

Data from the IDEXX Laboratories Reference Laboratory Network were retrospectively examined for feline heartworm testing trends in testing frequency, geographic bias, and prevalence for the years 2000--2006. Examination of the data supports the commonly held view that veterinarians do not embrace heartworm disease testing or prevention in cats to the same degree they do in dogs. Despite significant awareness and adoption of heartworm testing and prevention in dogs, we hypothesized that heartworm testing rates are lower for cats than for dogs despite a significant prevalence of feline infection. This is important because a perceived low rate of infection in cats is likely to manifest in a low adoption of testing and prevention. In reality, the overall feline heartworm antigen-positive rate is significant--on average 0.9% over the period studied--and in some regions was estimated to be as high as 4.6%. This compares with an average canine heartworm prevalence rate of 1.2%, a feline leukemia virus prevalence of 1.9%, and a feline immunodeficiency prevalence of 1.0%. Based on the low rate of testing and these prevalence rates, practitioners are routinely missing cases of adult feline heartworm infections and the recently defined heartworm-associated respiratory disease (H.A.R.D). Increased antigen testing would result in detection of a significant number of positive cases. In addition, this population of infected cats would represent the "tip of the iceberg" relative to the greater number of cats that have early infection or are at risk for infection.

Serological survey of Toxoplasma gondii, Dirofilaria immitis, Feline Immunodeficiency Virus (FIV) and Feline Leukemia Virus (FeLV) infections in pet cats in Bangkok and vicinities, Thailand.

The seroprevalence of Toxoplasma gondii, Dirofilaria immitis (heartworm), feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) infections was examined using serum or plasma samples from 746 pet cats collected between May and July 2009 from clinics and hospitals located in and around Bangkok, Thailand. The samples were tested for heartworm, FIV, and FeLV using a commercial ELISA. Of the 746 samples, 4.6% (34/746) were positive for heartworm antigen, 24.5% (183/746) had circulating FeLV antigen, and 20.1% (150/746) had antibodies against FIV. In addition, the first 348 submitted samples were tested for T. gondii antibodies using a modified agglutination test (MAT, cut off 1:25); 10.1% (35/348) were seropositive. Of the 348 cats sampled for all four pathogens, 11, 10, and 1 were positive for T. gondii antibodies and FIV antibodies, FeLV antigen, or D. immitis antigen, respectively. Of the 35 T. gondii-seropositive cats, 42.9% (15/35) were co-infected with at least one of the other three pathogens. The presence of antibodies to FIV was significantly associated with both age and gender, while FeLV antigen presence was only associated with age. In the case of FIV, males were twice as likely to be infected as females, and cats over 10 years of age were 13.5 times more likely to be infected than cats less than 1 year of age. FeLV antigen was more common in younger cats, with cats over 10 years of age being 10 times less likely to be FeLV positive than cats under 1 year of age. This is the first survey for these four pathogens affecting feline health in Thailand.

Serological study of selected vector-borne diseases in shelter dogs in central Spain using point-of-care assays.

We evaluated the prevalence of selected vector-borne diseases in 131 dogs in an animal shelter in central Spain using point-of-care assays (SNAP 4DX and SNAP Leishmania; IDEXX Laboratories, Westbrook, ME). The SNAP 4DX detects Dirofilaria immitis (Di) antigen and antibodies against Ehrlichia canis (Ec), Borrelia burgdorferi (Bb), and Anaplasma phagocytophylum (Aph); the SNAP Leishmania kit detects antibodies against Leishmania infantum (Li). Dogs were classified as healthy or sick based on physical examination, complete blood counts, and serum chemistry profiles. The prevalence of positive test results was as follows: Ec, 5.3% (n = 7); Aph, 19.0% (n = 25); Bb, 0%; Di, 0%; and Li, 5.3% (n = 7). Four dogs (3%) were coexposed to Ec and Aph, and three dogs (2.3%) were coexposed to Aph and Li. There was no statistically significant correlation between positive serology and clinical status (sick vs. healthy) or hematologic/biochemical abnormalities. The prevalence of Aph was the highest and is in agreement with a recent report in a dog shelter in northwestern Spain. These point-of-care assays may be more valuable as epidemiologic than as clinical tools.

Borrelia burgdorferi sensu lato species in Europe induce diverse immune responses against C6 peptides in infected mice.

The diversity of Lyme-borreliosis-inducing Borrelia species in Europe set high standards for the use of serodiagnostic test systems in terms of specificity and sensitivity. In the United States, the one-step C6 antibody test system based on the invariable domain IR6 of the VlsE molecule has been established as a successful diagnostic tool for testing canine samples. However, only a limited set of data are available regarding the antigenicity of the C6 peptides in an experimental murine model and sensitivity of the test regarding European Borrelia species. In order to investigate antibody reactions induced by these spirochetes, a total of 142 C3H/HeN mice were inoculated with Borrelia burgdorferi sensu stricto N40, B. garinii PBi, two isolates of B. afzelii, B. spielmanii A14S, B. valaisiana Rio6, B. valaisiana VS116, or B. lusitaniae. Infection of the mice was documented utilizing tissue culture and PCR. The IR6 sequences of B. burgdorferi sensu stricto B31, B. garinii IP90, and two B. afzelii ACAI strains have been used to synthesize and test additional C6 peptides. Compared to the well-established two-tiered test system, the results indicate that single C6 peptides derived from B. burgdorferi sensu stricto and B. garinii can be used in an enzyme-linked immunosorbent assay-based technique to detect murine antibodies induced by either agent. Little is known about the prevalence or pathogenicity of the B. afzelii strains in mammalian hosts, but our experimental data indicate differences in the C6 peptide test sensitivity for the detection of antibodies induced by different strains or isolates of B. afzelii.

Quantitative measurement of C6 antibody following antibiotic treatment of Borrelia burgdorferi antibody-positive nonclinical dogs.

The detection of antibody to the Borrelia burgdorferi C6 peptide by use of enzyme-linked immunoassays is a widely accepted method for the diagnosis of Lyme disease spirochete infection in dogs and in humans. Antibody to the C6 peptide is highly specific for B. burgdorferi and declines following treatment of dogs and humans exposed to B. burgdorferi. A quantitative assay for determining C6 antibody levels was developed and used to measure changes in antibody levels following antibiotic treatment of B. burgdorferi antibody-positive nonclinical dogs. One hundred thirty-two client-owned dogs were used in the study; 64 were negative, 53 of 68 positive animals received treatment, and 15 were untreated controls. Test sera were collected at 3, 6, and 12 months from seropositive dogs receiving treatment and untreated controls. Dogs in the treated group were assigned to moderate-to-high (> or =29 U/ml)- and low (<29 U/ml)-C6-level groups because the change in the C6 level after treatment was dependent on the level prior to treatment. There were significant declines in the 30 dogs with moderate-to-high initial C6 levels that exceeded the maximal declines of the untreated control dogs in all cases at 6 months (16 data points) and 12 months (29 data points) posttreatment. There was little change in C6 level following antibiotic therapy in the 23 dogs with low initial C6 levels. The quantitative C6 antibody test can be used to measure changes in C6 antibody levels following treatment of antibody-positive nonclinical dogs.