Seroprevalence of Canine Dirofilariosis, Granulocytic Anaplasmosis and Lyme Borreliosis of Public Health Importance in Dogs from India's North East

(2014) Seroprevalence of canine dirofilariosis, granulocytic anaplasmosis and lyme borreliosis of public health importance in dogs from India's North East, Veterinary World 7(9): 665-667. Abstract Aim: Vector-borne infections namely dirofilariosis, ehrlichiosis, anaplasmosis and lyme borreliosis are being recognized as emerging and/or re-emerging problems in dogs and man due to rapid extension of zoogeographical ranges of many causative agents through international tourism and increase mobility of dogs at national and international level towards meeting the demand for companion animals in the present day society. Anticipating such situation, a serological study was conducted in dogs from North East India to estimate the prevalence of zoonotically important Dirofilaria immitis, Anaplasma phagocytophilum and Borrelia burgdorferi along with Ehrlichia canis. Materials and Methods: Serological study was carried out using enzyme immunoassay in commercial SNAP 4DX ® test kit (Idexx Laboratories, USA). The study was conducted in 191 dogs comprising 82 pets, 57 stray and 52 working dogs owned by defence organizations. Results: The study revealed seroprevalence of mosquito-borne D. immitis (17.80%), tick-borne E. canis (22.51%) and A. phagocytophilum (4.71%) with an overall 41.88% prevalence of pathogens in single or co-infection. Serological evidence of tick-borne lyme borreliosis due to B. burgdorferi could not be established in dogs in the present study. Of the zoonotic species, highest prevalence of D. immitis was found in the stray dogs (22.80%) and that of A. phagocytophilum in pet dogs (6.09%). Conclusion: The results of the present serological study serve as baseline information on the prevalence of A. phagocytophilum in dogs reported for the first time in India and reaffirmation on the high prevalence of D. immitis and E. canis in the North East India.


Introduction
Dog, a multipurpose highly demanding companion animal in the present day society suffers from several vector-borne diseases caused by bacterial, viral and parasitic pathogens.Majority of these infections in the changing environment have attained emerging/ re-emerging and zoonotic status [1] due to rapid extension of their geographic distribution through travelling pets, working dogs owned by defence organizations and unabated dog trading at national and international levels [2,3].This has warranted monitoring and surveillance of diseases for better information to veterinarians and pet owners about their prevalence, risk of spread and public health importance.
Therefore, the aim of this study was to determine the seroprevalence of mosquito-borne Dirofilaria immitis and tick-borne Anaplasma phagocytophilum and Borrelia burgdorferi of zoonotic importance besides Ehrlichia canis in dogs from the North East India.

Study population
The study was conducted in 191 dogs comprising pets (82), working (52) and stray dogs (57) of different breeds, ages more than 6 months and either sex.The pet dogs owned by private owners and the working dogs of several defence organizations were selected from the population of dogs that were presented with different clinical illness at the Teaching Veterinary Clinical Complex, College of Veterinary Science, Guwahati, Assam during the year 2011 and 2012.Selection was done on the basis of medical history and presenting clinical findings, which included lethargy, depression, anorexia, fever, lameness, hemorrhages, pale mucous membrane, tiredness and weight loss.The stray dogs included in the study were randomly chosen from the animals captured time to time by the animal welfare organizations for sterilization under birth control program.

Method
Blood samples were collected in tubes containing ethylenediaminetetraacetic acid for enzyme linked immunosorbent assay in commercial SNAP 4DX ® (Idexx Laboratories, USA) test kits for qualitative detection of antibodies to A. phagocytophilum, B. burgdorferi and E. canis and D. immitis antigen.The test was performed as per manufacturer's protocol.Thin blood smears were prepared from the blood samples, stained with Giemsa and microscopically examined to correlate its findings with those of immunoassay for conclusive evidence.

Results
In the present study, overall 41.88% dogs tested positive for D. immitis antigen (17.80%) and antibodies to E. canis (22.51%) and A. phagocytophilum (4.71%).Exposure to single species pathogen was observed in 38.74% cases against 6.28% with dual infection (Figure -1).According to categories of dogs, highest exposure was recorded in stray dogs (52.63%), followed by working dogs (51.92%) and the least in the pet dogs (28.04%).Of the zoonotic species, highest record of D. immitis was found in stray dogs (22.80%) and that of A. phagocytophilum in pet dogs (6.09%).Evidence of B. burgdorferi was not recorded in any of the dog blood samples examined (Table -1

Discussion
The present study was conducted to understand the epidemiology of mosquito borne D. immitis and tick-borne E. canis, A. phagocytophilum and B. burgdorferi infection in dogs from the North East India to increase awareness among veterinary practitioners and the pet owners about their prevalence and risk of human exposure.Serological test based on enzyme immunoassay technology in a commercial kit SNAP 4DX ® with proven high degree of sensitivity and specificity [4,5] employed in the present study could detect 41.88% dogs positive to D. immitis antigen and antibodies against E. canis and A. phagocytophilum.A handful of studies conducted in different countries have revealed prevalence of these pathogens, including B. burgdorferi at varying rates according to geographical location [5][6][7][8].
Canine vector-borne diseases in India are reported to be far from clear [9].Limited studies conducted at different places revealed prevalence of Trypanosoma evansi, B. canis, B. gibsoni, D. immitis, Dirofilaria repens, H. canis, E. canis and A. platys [10,11].Present findings also confirmed the existence of these pathogens except T. evansi in this study region.However the rates of prevalence of D. immitis and E. canis in all categories of dogs were found much higher than those reported from other parts of the country.This might suggest maximum confinement of heartworm infection in India's North East [9] and use of SNAP 4DX ® which is the most efficient kit for serodiagnosis of E. canis compared to detection of morula by microscopy [5].Seroprevalence of A. phagocytophilum recorded in this region provides a new insight since the pathogen has not been reported earlier from India.Evidence of lyme borreliosis due to B. burgdorferi in dog could not be established in the present investigation although its prevalence in human population has been recorded in India including the North east region [12].
There is ample literature to suggest serological assay as an efficient tool that provides more accurate result compared with microscopy in diagnosis of hidden or past infections [13,14].Serological findings supported by microscopic detection of corresponding parasite stages in Giemsa stained blood smear also helped to ascertain the disease status by overcoming the complexity of diagnosis from clinical symptoms, which were not pathogen specific and mimic each other as reported elsewhere [4,15].Consistent with earlier reports made from this region [16,17] on the high rates of prevalence of haemoparasites, the present findings of serology supported by microscopic study suggest that this region has ideal biotope for the vector-borne pathogens.Endemic situation with mosquito-borne canine dirofilariasis in this region warrants a thorough investigation in the human population for the risk of zoonosis, which has been reported in India and elsewhere [18][19][20].

Conclusion
The results of the present serological study serve as baseline information on the prevalence of A. phagocytophilum in dogs reported for the first time in India and reaffirmation on the high prevalence of D. immitis and E. canis in the North East India.

Table - 1
: Seroprevalence of D. immitis, E. canis, A. phagocytophilum and B. burgdorferi in dogs from North-East India.
a One dog seropositive to D. immitis and E. canis, b One dog seropositive to D. immitis and A. phagocytophilum, c One dog seropositive to E. canis and A. Phagocytophilum.D. immitis=Dirofilaria immitis; E. canis=Ehrlichia canis, A. phagocytophilum=Anaplasma phagocytophilum, B. burgdorferi=Borrelia burgdorferi