In vitro study on thiabendazole action on viability of Ascaris lumbricoides (Lineu, 1758) eggs Estudo in vitro da ação do tiabendazol sobre a viabilidade de ovos de Ascaris lumbricoides (Lineu, 1758)

The in vitro activity of thiabendazole on Ascaris lumbricoides eggs, which were recovered from uteri of worm excreted after chemotherapeutic treatment, was studied. Four concentrations of the drug were used: 1 – 2.5 – 5 – and 10 ppm during 24, 48 and 72 hours of exposure. Subsequently, the eggs were centrifuged, washed three times and H2SO4 0.1N was added. The eggs were maintained in an incubator for 20 days at 28 0 C. Finally, the percentage of embryonated eggs was determined under a lightmicroscope at a 100X magnification. After 48 and 72 hours of thiabendazole exposure, at a concentration of 10ppm, the drug showed complete inhibition of egg embryonation. Key-words: Ascaris lumbricoides. Thiabendazole. Ovicide. Resumo Foi estudada, in vitro, a ação do tiabendazol, contra ovos de Ascaris lumbricoides, retirados de úteros de vermes eliminados após tratamento. Foram utilizadas quatro concentrações da droga: 1 – 2,5 5 e 10 ppm em três diferentes períodos de tempo: 24, 48 e 72 horas. Decorridos estes tempos a suspensão com os ovos foi centrifugada, lavada por três vezes com água destilada, adicionada de solução de H2SO4, 0,1N e mantida em estufa a 28°C por 20 dias. Em seguida, os ovos foram levados ao microscópio óptico, no aumento de 100X, para observação do percentual de embrionamento. Na concentração de 10ppm, nos tempos de 48 e 72 horas de exposição à droga, verificou-se completa inibição do embrionamento dos ovos. Palavras-chaves: Ascaris lumbricoides. Tiabendazol. Ovicida. 1. Laboratório de Helmintoses Intestinais do Centro de Pesquisas René Rachou da Fundação Oswaldo Cruz. Belo Horizonte, MG, Brasil. 2. Laboratório de Epidemiologia e Antropologia Médica do Centro de Pesquisas René Rachou da Fundação Oswaldo Cruz. Belo Horizonte, MG Address to: Dr. Cristiano Lara Massara. Centro de Pesquisas René Rachou/FIOCRUZ. Caixa Postal 143, 30190-970 Belo Horizonte, MG. Telefax 55 313295-3115 e-mail: [email protected] Recebido para publicação em 11/7/2000. Parasitic diseases are an important public health problem in most developing countries. Latin American and African populations are found to be parasitized by at least one helminth species18. It is estimated that there are 2 billion people at risk of helminth infections. Of these, 250 million are infected by Ascaris lumbriocides, 46 million by Trichuris trichiura, 151 million by hookworms and 56 million by Strongyloides stercoralis1 7 15 17. Gastrointestinal parasitic diseases are highly prevalent in Brazil as they are closely associated with poor living conditions, such as inadequate housing, lack of food and basic sanitation as well as low educational level, leading to failure to perform basic hygiene. Several research groups 4 9 10 11 12 16 20 have been developing, testing and using drugs which act both on individual treatment and interrupting helminthes life cycle. Current anthelmintics are only used to temporarily decrease the parasitic prevalence indices. Since the drug effects are not ovicidal, the eggs are regularly excreted on the ground through the feces, leading to new infections16 19. By using thiabendazole in pigs experimentally infected with Ascaris suun, Egerton 4 observed morphological changes in the eggs and inhibition of embryonation. Kutsumi et al12 added thiabendazole to the nightsoil and verified a decrease in human hookworm, A. lumbricoides and T. trichiura transmission in three areas, compared with non-treated areas. Goulart et al treated egg cultures of Ascaris lumbricoides, T. trichiura and Ancylostoma caninum with thiabendazole, using 1, 10 and 100mg doses and demonstrated the ovicidal inefficiency of this anthelmintic for the first two parasite species.