The fatal case of an autochthonous heartworm disease in a dog from a non-endemic region of south-eastern Slovakia

In December 2019, a 7-year-old 50 kg male Tibetan Mastiff dog was referred to the veterinary hospital at the University of Veterinary Medicine and Pharmacy (UVMP) in Košice because of acute weakness and apathy. He suffered from anorexia and vomiting. The clinical examination revealed: an elevated body temperature (39.8 °C), anaemic mucous membranes and pain in the abdomen. Epistaxis from both nostrils was also observed. The breathing frequency and pulse were normal. The lymph nodes were not enlarged, auscultation of the heart was normal, without any murmurs, and the respiratory sounds were normal. No jugular vein pulsations were observed. During the hospitalization, the patient was found to be oliguric.

A blood examination and ultrasonography (USG) of the abdomen were performed. The haematological examination revealed a leucocytosis and neutrophilia; biochemistry showed an elevated alkaline phosphatase. Other parameters were within the normal reference ranges. However, the creatinine and urea levels started to rise sharply during following days. The USG exam revealed an increased liver hyperechogenicity, mild hepatomegaly with highlighted portal veins and the presence of the sediment in the gallbladder. The stomach contractions and intestine peristalsis were slowed down, with fluid stagnation in the stomach. The caecum was filled with fluid as well as some segments of the small intestine. The urinary bladder was distended with significant sediment inside. The prostate and both of the kidneys were of normal size and echogenicity.

Canine pancreatic lipase test (SNAP® cPL™ Test IDEXX Laboratories, Inc., Westbrook, ME, USA) was performed with positive results. The SNAP® Lepto test (IDEXX Laboratories, Inc., Westbrook, ME, USA) for the detection of Leptospira-antibodies was negative.

The specific gravity of the urine was measured with a value of 1018 kg/m³; the pH of the urine was 6.0. Leukocytes, erythrocytes, squamous and tubular cells were detected in the urinary sediment. The dog was also tested using a rapid test system registered for the detection of D. immitis antigen and specific antibodies to synthetic peptides of Anaplasma phagocytophilum/Anaplasma platys, Borrelia burgdorferi s.l., Ehrlichia canis and Ehrlichia ewingii (SNAP® 4Dx® Plus, IDEXX Laboratories, Inc., Westbrook, ME, USA) with positive results for D. immitis. Subsequently, the diagnosis was confirmed at IP SAS, Košice, using the PCR approach. Briefly, DNA was extracted from the blood using DNeasy Blood and Tissue Kit (Qiagen, Germany) and subsequently fragments of cytochrome c oxidase were amplified with D. immitis and D. repens specific primers using conventional PCR (Rishniw et al., 2006).

The cardiologic examination was planned, however, the condition deteriorated and dyspnoea appeared. The X-ray revealed an alveolar pattern in the cranial lung lobes and the heart silhouette was not visible due to changes in the lungs. The dog died after 5 days and no other examinations could be performed. The dog was submitted for post-mortem examination and adult D. immitis worms were found in the right heart ventricle, and several specimens were identified in the pulmonary arteries (Fig. 1). In addition, pulmonary oedema was discovered and the right ventricle was dilated. The necropsy findings included: chronic interstitial nephritis and chronic cystitis, acute catarrhal jejunitis, sediment in the gallbladder and icterus. Cardiovascular and respiratory failure in connection with kidney damage was assigned as an immediate cause of the death.

Fig. 1

Another dog from the same owner was referred to our clinic several days later. This 7-year-old female Tibetan Mastiff, was born in the same litter as dog 1 and they were kept together in the same household. This dog did not manifest any signs of the heartworm disease, but numerous microfilariae were detected in a blood smear. Additionally, a SNAP® 4Dx® Plus Test was performed for the detection of circulating D. immitis female antigen and was positive. The DNA analysis unambiguously confirmed the heartworm infection. The results of further haematological and biochemical examinations yielded values within the normal reference ranges. The value of renal biomarker SDMA (symmetric dimethylarginine) was 8 μg/dL (reference interval for adult dogs: 0 – 14 μg/dL) and the echocardiography revealed no abnormalities.

An alternative therapeutic protocol with macrocyclic lactones and doxycycline was proposed in the female patient due to the unavailability of the melarsomin dihydrochloride (Savadelis et al., 2017; ESDA, 2017) regimen. Eventually, the treatment selected involved monthly applications of imidacloprid/moxidectin (10 %/2.5 %) for 9 months and doxycycline administration at a dose of 10 mg/kg twice daily for the first 30 days. Additionally, prednisone was administered at a dose of 0.5 mg/kg twice daily for the first week, then it was reduced to 0.5 mg/kg once daily for another week and subsequently the dose of 0.5 mg/kg every 48 hours was given during the third and fourth weeks.

Currently (in February 2020), the treatment is still in progress and the patient is monitored at the University Hospital of UVMP in Košice.