DIROFILARIOSIS IN DOG CASE REPORT M.S. ILIE, GH. DĂRĂBUŞ, ROBERTA CIOCAN, IONELA HOTEA, K. IMRE, S. MORARIU, NARCISA MEDERLE, ALINA ILIE, D. MORAR Faculty of Veterinary Medicine Timisoara, 119 Calea Aradului, 300645, Timisoara, Romania E-mail: marius.ilie@fmvt.ro Summary This work deals about some pathological manifestations found in dogs dirofilariosis. The dogs were examined in the Parasitology and Parasitological diseases and Small Animal Pathology clinics of the Faculty of Veterinary Medicine, Timisoara, Romania. The pathological manifestations were studied on 4 dogs of different sex, breed and age. In chronic evolution of heartworm disease in most infected dogs do not show clinical signs. Serological tests for heartworm disease can be negative in non-endemic areas and that s why additional methods are compulsory.the application of prophylactic measures in dogs throughout the period of mosquito activity can be decreased incidence and dissemination of dirofilariosis. Key words: dirofilariosis, dog, diagnostic, pathological manifestation Dirofilariosis is a disease caused by filarial worms of the genus Dirofilaria (12). Filarial nematodes are common parasites of many vertebrates (1, 5). The nematodes of genus Dirofilaria belong to family Onchocercidae and subfamily Dirofilariinae of the order Spirurida (1, 8). This genus consists of 27 valid species, and 15 species of questionable validity (2, 12). The genus Dirofilaria is divided in two subgenera. The subgenus Dirofilaria includes Dirofilaria immitis and the subgenus Nochtiella includes Dirofilaria repens (8). In European dogs, the most common species of filariae are Dirofilaria immitis, D. repens and Acanthocheilonema (syn. Dipetalonema) reconditum. Species found in the subcutis such as Dirofilaria repens or Dipetalonema reconditum were considered nonpathogenic (3, 9). D. immitis and D. repens are transmitted by over 60 common mosquito species. The intermediate hosts of D. reconditum are fleas and lice. Because dirofilariosis is a zoonotic helminthosis and are imprecisely diagnosed we proposed to present some pathological manifestations in dogs dirofilariosis. Materials and methods The dogs were examinated in the Parasitology and Parasitological diseases and Small Animal Pathology clinics of the Faculty of Veterinary Medicine, 59
Timisoara, Romania. The pathological manifestations were studied on 4 dogs of different sex, breed and age. For diagnosis venous blood was collected from domestic dog from Timis County. Blood samples were collected into 3 ml EDTA tubes from canine patients. Canine dirofilariosis was diagnosed by identification of microfilariae or specific antigen testing. Filarial infection in dogs can be diagnosed through morphological observation of circulating microfilariae, detection of circulating antigens, histochemical or immuno-histochemical staining of circulating microfilariae, or through molecular approaches (3). Microfilariae were detected using direct examination of fresh blood drop and microfilariae identification was confirmed by modified Knott test and acid phosphatase stain (7, 14). Several immunochromatographic kits are commercially available to detect the presence of adult female circulating antigens in serum, plasma and whole blood of dogs and cats. Most are very specific, quite sensitive, rapid and easy to be performed. Detection of the antigen of sexually mature females in canine blood serum was performed Speed DIRO / HEARTWORM for detection of Dirofilaria immitis adults (18). Results and discussions First case. A female, 5 years old, German shepherd dog was come in Pathology of Small Animals Clinic with fever (40.4 ºC) which do not decreased below antibiotics. The dog had never been routinely investigate or treated with heartworm preventatives and do not have antecedents related by outside to town movements. At blood exam was distinguished microfilaria. By Speed DIRO / HEARTWORM antigen of sexually mature females in canine blood serum were positive for Dirofilaria immitis adults. Thoracic radiographs do not showed abnormalities. Second case. In September 2008, at Faculty of Veterinary Medicine Timisoara a Coker American dog was presented. A female, 2 years old, was hyperthermia, prostration, dyspnoea, hyper salivation, tonsillitis, retropharyngeal lymphonodular hyperplasia. The temperature was varied between 39.2º C, morning, and 40.5º C, evening. The increased values of temperature keep on during antibiotic therapy. The dog was anorexic and presented respiratory signs. Another sign observed was polyarthritis with pain and joint swelling at all legs sometime alternatively, and difficult movements. The dog was tested for Dirofilaria immitis. At smear blood exam were distinguish microfilariae and at Speed DIRO / HEARTWORM result was positive. Third case. A 7 years old, Amstaff breed, male, was presented in our clinic in January 2009 for routine examination. Though appetite is present the dog loss the weight, in last two months. 60
The dog was taken from a town near to Timisoara and is walked by the owner on an open field where there are many small water pools. Following the general examination it was observed only an increased volume of poplitei lymphonods. At the blood drop examination there were detected microphylarias and the result of the Speed DIRO / HEARTWORM test was positive. Fourth case. On March 2009 a dog was investigated and there were present microfilariae at the blood drop test, but Speed DIRO / HEARTWORM test the result turned out to be negative. The examined dog is a male of two years of age with an unknown background. The dog has exhibit no clinical symptoms, is non-feverish (39.1 39.2º C), has a good appetite and is very active. Clinical signs of heartworm disease may not be recognized in the early stages, as the number of heartworms in an animal tends to accumulate gradually over a period of months and sometimes years and after repeated mosquito bites (15). Serological tests for heartworm disease are frequently negative in nonendemic areas because of the microfilariae belong to species other than D. immitis, the persistence of microfilaremia after natural or pharmacological death of adult worms, and the low number of D. immitis adults in the pulmonary arteries of the host. The presence of a single female and/or one too many males is hardly detected by these tests (13). In our study, microfilariae identification was confirmed by acid phosphatase stain in all four positive samples. Some authors (4, 7, 10, 11) reported that the clinical evolution of heartworm disease in dogs is usually chronic. Most infected dogs do not show any signs of the disease for months or years, depending on many factors such worm burden, individual reactivity etc. Recently infected dogs may exhibit no signs of the disease, while heavily infected dogs may eventually show clinical signs, including a mild, persistent cough, reluctance to move or exercise, fatigue after only moderate exercise, reduced appetite and weight loss (15). Dogs show no clinical signs of heartworm infection during the first 6 month post infestation (prepatent period) prior to the worms' maturation, and current diagnostic tests for the presence of microfilariae or antigens cannot detect prepatent infections. Rarely, migrating heartworm larvae get "lost" and end up in unusual sites such as the eye, brain, or an artery in the leg, which results in unusual symptoms such as blindness, seizures and lameness. But normally, until the larvae mature and congregate inside the heart, they produce no symptoms or signs of illness (14, 16). Less than 25 worms in a dog's heart may cause no symptoms at all, so a dog can be infected and passing the parasite on to mosquitoes without anyone knowing there s anything wrong. If there are 60 or more worms in the heart and pulmonary artery, there are likely to be circulation problems with damage to the 61
heart, liver, and kidneys, and more than a 100 heartworms is associated with blood circulation blockage (6). Signs of the disease develop gradually and may begin with a cough followed by dyspnea, weakness, and occasionally, by lipotimias after exercise or excitement. Can often be detected abnormal pulmonary sounds and second heart sound, cardiac murmurs over the right side of the thorax and abnormal cardiac rhythm, swelling of the abdomen (and sometimes the legs). Another signs of the disease such anorexia, weight loss, and dehydration are usually noted. Sudden death rarely occurs and usually happens following respiratory distress or cachexia. In the course of chronic disease, acute signs may occasionally occur. Severe spontaneous thromboembolism following the natural death of many heartworms can cause dogs to present acute, life-threatening dyspnea and hemoptysis. In small dogs, another common manifestation is caval syndrome. (a syndrome of cardiovascular collapse, caused by large numbers of heartworms in the right heart and vena cava) (7, 11). Occasionally adult worms have been observed in the brain where they invade the lateral ventricle, or in the meningeal arteries with subsequent occlusion. The clinical course is characterized by intermittent convulsion, blindness, ataxia, behavioral changes and circling (17). Dirofilariosis was originally considered a disease of strict veterinary importance but it has been recognized as an emerging zoonosis (4, 7, 12) and is necessary to protect the health of animals and people. Conclusions Clinical signs of heartworm disease may not be recognized in the low infestations in dogs examined. The most infected dogs with chronic evolution of heartworm disease do not show clinical signs. Serological tests for heartworm disease can be negative in non-endemic areas and that s why additional methods are compulsory. The application of prophylactic measures in dogs throughout the period of mosquito activity can be decreased incidence and dissemination of dirofilariosis. References 1. Anderson, R.C., Nematode Parasites of Vertebrates - Their Development and transmission. CAB International, Wallingford, Oxon, UK, 2000. 62
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