Aspectos biológicos da inoculação experimental e atividade malaricida da 4-(6-mercaptopurina)-7-cloroquinolina em Gallus gallus Linnaeus, 1758 experimentalmente infectados por Plasmodium (Novyella) juxtanucleare Versiani & Gomes, 1941 (Apicomplexa, Plasmodiidae)

Abstract

Plasmodium juxtanucleare is the agent of the avian malaria that occurs in some states of Brazil. This malaria is related to several clinical signs and it can cause damages in the poultry section. The aviary model was already used for the investigation of drugs in the combat to the malaria and nowadays the model more used is the Plasmodium berghei in rodents. The search for anti-malarial drugs is of extreme importance. The aim of this study was to accomplish experimental infections of Plasmodium juxtanucleare in Gallus gallus and to test a substance recently synthesized, the 4-(9H-purin-6-ylthio)-7-cloroquinoline, derived of the cloroquine, to verify their effects on the avian malaria and to improve the aviary model for these types of tests. For a bird donor's encounter, two chicken farms were visited in the Juiz de Fora city and blood smears made in 30 hens. The prevalence was 100%. Among the 30 examined hens, six with the largest parasitemia values had been acquired and taken to the laboratory. To verify which the best day to retreat the blood to infected hens, five of the six hens received only dose of the imunossupressor substance (metilprednisolon acetate) and one served as control. The parasitaemia of the hens was accompanied by 26 days after the day of the imunossupression, through blood smears prepared each two days. The weight and corporal temperature were checked and made blood hematocrits. It was verified that to the 10th day powder-imunossupression it happened parasitaemia pick. There were fall of body weight and correlation with the parasitaemia. There was a little variation in the body temperature and hematocrite and there was not correlation of these with the parasitaemia. In other eight acquired hens in commercial house with 15 days old, experimental infections were accomplished with blood inoculated through intramuscle and intraperitoneally in the 0,3mL and 0,5mL for the two routes. During one month the hens had the value of parasites accompanied to compare which the most effective route and difference among the doses tested in the establishment of the infection. Significant difference was not observed among the xvii doses but it was possible to verify that the infection through intraperitonial reaches the parasitemia pick more quickly, with higher averages of parasites, however to the end of the experiment the total number of parasites differed hardly between the doses and routes. To test the effect a derived drug of the cloroquine, 45 chicks were infected, white Leghorn, through intramuscle route . The hens were separate in four experimental groups, 15 chicks for group (Group1 - no infected, Group 2 - infected and without treatment, Group 3 - infected and treated with the cloroquine and Group 4 - infected and treated with derived of the cloroquine) The drug was administered four consecutive days in the 100mg/Kg of alive weight dose. For the evaluation of the antimalarial effect of the drug, the hens had the number of parasites accompanied by blood smears done each two days after the tenth day of the inoculation. Also the weight and corporal temperature were checked each two days and hematocrit four days. Derived of the cloroquine had antimalarial activity, reducing the number of parasites and maintaining the lowest parasitaemia in relation to the group not treated and to the group treated with cloroquine.