Clinical, haematological, treatment and molecular evaluation of ehrlichial infections in dogs in Nairobi and its environs
Ehrlichiosis and Anaplasmosis are tick borne diseases with important zoonotic and public health implications. Although reported globally, data on apparent prevalence, clinical, haematological and treatment outcomes and molecular characteristics of ehrlichial infections in dogs in Kenya is scant. A study was therefore designed with the objectives to retrospectively determine the clinical features and treatment of ehrlichiosis in dogs; to evaluate clinical, haematological and biochemical features and treatment outcomes in dogs with ehrlichiosis; and to determine the molecular profiles and apparent prevalence of canine ehrlichiosis in Kenya. The retrospective study component entailed review of clinical and treatment records of 514 dogs diagnosed with ehrlichiosis at the Small Animal Clinic (SAC), Faculty of Veterinary Medicine, University of Nairobi between 1993 and 2006. The prospective study comprised evaluation of clinical, haematological, biochemical and treatment data on ehrlichial infections in dogs presented at the SAC. Identification of the ehrlichial species was performed using Polymerase Chain Reaction (PCR) with genus-specific and species specific primers based on ehrlichial 16S rRNA genes and sequence analyses. Data were analysed using descriptive statistics and independent t-test at a confidence interval of 95% (p≤0.05).Males were over-represented at 54.4% among the 479 dogs diagnosed with ehrlichiosis, with a large proportion of affected breed being the German shepherd dog (42.6 %).Clinical findings included lethargy, anorexia, fever, panting, lymphadenomegaly, pallor and congestion of mucous membranes, pounding heart, harsh lungs, vomiting, tender dogs suffering from ehrlichiosis and was observed in 65.3% and in 59.3 % of cases in the prospective and retrospective studies respectively. Congestion of mucous membranes was the most frequently observed sign and was reported in 55.4% and 48.7% of the dogs diagnosed with ehrlichiosis in the prospective and retrospective studies respectively. Pale mucous membranes were observed in 16.4% and 21.3% of the cases in the prospective and retrospective studies respectively. Haematological and biochemical parameters were significantly increased (p<0.05) (mean lymphocyte counts, and haematocrit). Although erythrocyte and thrombocyte counts and mean haemoglobin concentration were increased, these were not statistically significant. The mean granulocyte counts decreased significantly (p<0.05) following diagnosis and 14 days post-treatment. Significant (p<0.05) increases were observed in serum albumin and calcium levels in dogs diagnosed with ehrlichiosis in this study. Treatment resulted in clinical improvement, noted by resolution of anaemia, and altered haematological parameters, including significantly elevated Packed Cell Volume (PCV) (p<0.05). Congestion of mucous membranes reduced from 55.4% to 27.7%. Imidocarb dipropionate was the most preferred treatment (82.6 %), compared to Doxycycline (2.8%) or a combination of the two drugs (14 %). Although 49.1% of treated dogs reportedly recovered, 43.5% were lost to follow up 14 days post-treatment. Recovery following treatment with Imidocarb dipropionate was very high, as only 7.3% of dogs did not show clinical improvement. Molecular analysis revealed 58.6% (113/192) of dogs had positive amplification of ehrlichial DNA by PCR using primers ECC and ECB that amplify a sequence of the 16S rRNA gene of Ehrlichia and Anaplasma genera. Of the positive cases, 42.5% (48/113) were positive for Ehrlichia canis using the species specific primers HE3 and ECANS5, 5.3% (6/113) were positive for Ehrlichia chaffeensis with the species specific primers HE1 and HE3 and 1.8% (2/113) was positive for Anaplasma platys with the species specific primers PLATYS and EHR16SR.The most consistently observed clinical features in Ehrlichia canis infected dogs were lymphadenopathy, congestion of mucous membranes, inappetence, panting, loose hair, lethargy, vomiting, wasting, ocular discharge and diarrhoea. Signs for Ehrlichia chaffeensis infection included lethargy, lymphadenopathy, congestion of mucous membranes and inappetence; these were consistently present in affected dogs. On the other hand, signs of Anaplasma platys infection included lethargy, lymphadenopathy, ocular discharge, inappetence, panting, pounding heart, harsh chest, loose hair and wasting. The most commonly observed clinical signs in ehrlichiosis and anaplasmosis included lethargy, lymphadenopathy, pallor and congestion of mucous membranes, inappetence, loose hair, wasting, ocular discharge, harsh lungs and panting. Congestion of mucous membranes, lymphadenopathy, lethargy and inappetence were most consistently observed in dogs with ehrlichiosis. The study identified two additional ehrlichial species; Ehrlichia chaffeensis and Anaplasma platys, in Kenya, previously not reported. The study has also established the molecular identity of Ehrlichia canis, Ehrlichia chaffeensis and Anaplasma platys in dogs in Kenya, previously not reported. These findings confirm the zoonotic importance and public health implications of canine ehrlichiosis. Further investigations are recommended to determine the molecular epidemiology of ehrlichial infections in animals and humans in the region. It is also noted that congestion of mucous membranes is an important clinical sign in canine ehrlichiosis. The clinical presentation is not specific but congestion of mucous membranes, lymphadenopathy, lethargy and a history of inappetence coupled with thrombocytopenia form good inclusion criteria for a tentative diagnosis of ehrlichia infection where diagnostic services are limited.