PREVALENCE OF DIROFILARIA IMMITIS IN DOGS IN NIGERIA
The study on prevalence of Dirofilaria immitis was conducted in Zaria. A total of three hundred and seventeen dogs were examined from seven sampling sites; Samaru, Sabon Gari, Tudun Wada, Wusasa, Basawa, Kongo and Gyellesu from April to December 2012. 5mls of blood from the branchiocephalic vein was aseptically collected from each dog and was stored in sample bottle containing ethylene diamine tetra acetic acid (EDTA, 1mg/ml) and were transported to the laboratory in a cold box and analyze immediately on arrival, using modified knotts method. The overall prevalence of confirmed cases of Dirofilaria immitis infection in the dog population in Zaria was (48) 15.1%. Age specific prevalence showed that, infection was detected throughout the age 1 – 2 years old to 9 years above. Although the 1 – 2 years showed a high rate of infection in 66 dogs (21.2%) than the other ages respectively. The male dogs were relatively more infected than the females, 40 (81.9%) and 8 (8.3%) respectively. The disease was detected in all the sites. The foreign breeds were found to be free from the infection, these is probably due to the fact that special care are given to them. Prevalence was higher in un-caged and caged dogs. 34 (15.2%) and 14 (14.9%) respectively. There was not significant difference (p>0.05) in prevalence. A higher percentage of the positive cases showed low haemoglobin level 8 (21.6%), The reason could be that the infection causes anemia which in turn affects the level of hemoglobin likewise the total protein count 16 (13.2%). WBC count increased in positive cases which is indicative of Dirofilaria infection while the RBC is low in positive cases 7(14.8%).These indicates that the presence of the parasite does not affect the RBC. It not significant (p > 0.05) in blood counts Differential count of the WBC showed that the presence of the infection led to the release of a greater number of white blood cells such as Eosinophils, Lymphocytes, Monocytes and Neutrophils.
Analysis of the blood parameters showed positive correlation between the packed cell volume and haemoglobin, packed cell volume and red blood cell, haemoglobin and red blood cells, while the Neutrophil and lymphocytes showed negative correlation. The result of the study shows that Dirofilaria immitis infection is prevalent among dogs in Zaria, and indicates that D. immitis infection may be of public health concern then wither to envisaged .
1.1 Background of Study
Dirofilaria is a nematode parasite that is widely enzootic in carnivores especially dog. It is of the family filariidae (Soulsby, 1982). There are two known species of importance in dogs: Dirofilaria repens (D. repens) and Dirofilaria immitis (D. immitis), of which D. immitis is more important and is commonly called the dog heart worm. The adult worms are found in the right ventricle and pulmonary arteries of dogs and mammals (Gerald and Larry, 1989; Urguhart et al., 2003) and are responsible for delabitating condition known as canine heart worm (CHW) disease or dirofilarosis. Dirofilarosis cause by D. immitis is zoonotic and is transmitted by the mosquito vector (Urguhar et al., 2003).
Heartworms go through several live stages before they become adults to infect the pulmonary artery of the host animal. The worms require the mosquito as an intermediate host in order to complete their life cycle. The rate of development in the mosquito is temperature dependent, requiring approximately two weeks of temperature at above 27oC (80oF). Below a threshold temperature of 14oC, development cannot occur, and the cycle will be halted (Knight, 2000). As a result, transmission is limited to warm months and duration of the transmission season varies geographically. The period between the initial infection when the dog is bitten by a mosquito and the maturation of the worms into adults living in the heart takes six(6) to seven(7) months and its known as the “prepatent period”.