Clinical and Laboratory Profile of Dogs Seroreactive to Ehrlichiosis Treated at the Veterinary Medical Teaching Hospital in Niterói, State of Rio de Janeiro, Brazil

Abstract

Background: Ehrlichiosis is a tick-borne disease highly prevalent in Brazil, and is relevant in canine clinical practice due to its high morbidity and mortality. Its clinical signs are nonspecific and its phases are acute, lasting 2 to 4 weeks; subclinical, i.e., asymptomatic; and chronic, resembling an autoimmune disease. The purpose of this study was to identify the occurrence of reactivity to Ehrlichia canis of bitches treated at the Veterinary Medical Teaching Hospital of the Universidade Federal Fluminense (UFF) - Niterói, RJ, Brazil, based on serological examination by iELISA, and to compare the hematological, biochemical, urinary protein-creatinine and urinary density profiles of reactive and non-reactive animals. Materials, Methods & Results: This study involved solely bitches, regardless of breed, starting at 1 year of age. One hundred and thirty bitches, 1 to 16 year-old (mean age 7.02 ± 4.00), weighing 1.5 to 50 kg (mean weight 12.12 ± 10.65) were subjected to clinical examination and abdominal ultrasound. Complete blood count, biochemical measurements, urinalysis and serology for E. canis were also performed. The serum was used in the iELISA to identify immunoglobulin G (IgG), using a canine Ehrlichia Imunotest® diagnostic kit (Imunodot®, Jaboticabal, SP, Brazil) according to the manufacturer’s instructions. Sixty animals (46.20%) were reactive to E. canis. According to their owners, only 5 (8.3%) of the 60 seroreactive animals had a history of tick-borne disease. The most common profile was that of mixed breed animals living with their owners, older than 7 years, who had not been treated preventatively with specific drugs against ectoparasites. Laboratory tests showed significant differences between groups in terms of total protein (TP), and calcium and urinary protein-creatinine ratio (UPC). TP and UPC were elevated in the non-reactive group, while the only significant change in the reactive group was mild hypocalcemia. In this study, 30% (18/60) of the bitches were seroreactive to E. canis and had hypocalcemia. Of these, 50% (9/18) had a UPC above 0.5. Furthermore, 66.7% (12/18) of this group with hypocalcemia also showed urine density (UD) of less than 1024. Among these 18 bitches, 5 had both alterations, i.e., UPC > 0.5 and UD < 1024.Discussion: In this study, a high prevalence of bitches seroreactive to Ehrlichia canis was observed, despite the absence of clinical and/or laboratory signs indicative of the disease. In the investigation of IgG class antibodies, it is not possible to determine the exact time of infection, and titers may remain high for a period of more than 11 months, even after treatment and elimination of the bacterium. The fact that most seroreactive bitches showed no symptoms compatible with the disease either before or during the study suggests that they were in the subclinical phase of ehrlichiosis. The main reason for calcium metabolism disorders is a phosphorus imbalance, a condition that occurs in kidney diseases. Isosthenuria reflects the kidney’s inability to concentrate urine. This finding may be one of the first clinical manifestations of chronic kidney disease (CKD), especially in dogs. On the other hand, the UPC ratio may increase with the progression of CKD. The presence of hypocalcemia, isosthenuria and increased UPC associated with seroreactivity suggests that infection by E. canis may be associated with the onset of CKD. Veterinarians should keep in mind the complexity of the pathophysiology of ehrlichiosis to ensure the disease is not underdiagnosed in any of its phases, thereby ensuring the correct treatment is provided. Such awareness is expected to reduce the chronicity of the disease and underlying sequelae among dogs.Keywords: Ehrlichia canis, serology, tick, clinic, renal.Descritores: Ehrlichia canis, sorologia, carrapato, clínica, renal.Título: Perfil clínico e laboratorial de cadelas sororeativas para erliquiose tratadas em um Hospital Veterinário Universitário em Niterói, Estado do Rio de Janeiro, Brasil