RESUMO
Immunization against the protozoan Theileria parva by infection and treatment has proved to be very efficient for the control of East Coast fever, an acute and often-fatal lymphoproliferative tick-borne disease of cattle in Eastern, Central and Southern Africa. The immunizing dose of live T. parva sporozoites used in this method is usually determined by in vivo titration. An alternative in vitro method of quantification of sporozoites in whole tick-derived stabilates is proposed. The method consists of incubating serially diluted T. parva stabilates with bovine peripheral blood lymphocytes, the host cell that is infected naturally. Allowing the cultures to incubate undisturbed for the full cultivation period (10 days) reduced the variability among replicate titrations. Fungal contaminations were avoided by centrifuging stabilates at 400 g prior to the incubation, which did not precipitate sporozoites significantly. Fungistatics, Nystatin and Flucytosine, did not appear to interfere with the in vitro development of T. parva but their effect on fungal growth was limited. In vitro titration data were compared to in vivo infection data for 2 stabilates. In vitro titration of T. parva sporozoites should allow more ethical and efficient research on the preparation and storage of T. parva tick-derived stabilates.
Assuntos
Imunização/veterinária , Theileria parva/imunologia , Theileriose/imunologia , Carrapatos/parasitologia , Animais , Antifúngicos/farmacologia , Bovinos , Flucitosina/farmacologia , Imunização/métodos , Leucócitos Mononucleares/imunologia , Modelos Logísticos , Nistatina/farmacologia , Reprodutibilidade dos Testes , Theileriose/parasitologia , Theileriose/prevenção & controle , Doenças Transmitidas por Carrapatos/imunologia , Doenças Transmitidas por Carrapatos/parasitologia , Doenças Transmitidas por Carrapatos/prevenção & controle , Doenças Transmitidas por Carrapatos/veterináriaRESUMO
Lyophilisation of Theileria parva sporozoite stabilates used for immunisation of cattle against East Coast fever would greatly improve vaccine storage and delivery. We report three attempts to lyophilise and resuscitate the sporozoites of T. parva. Sporozoites survived lyophilisation and were effective for immunisation. Lyophilised stabilate survived for 2 weeks at 5 degrees C and for 12 weeks at -20 degrees C. Although the viability of the stabilates was severely reduced during lyophilisation, this work suggests that this method has potential and should be considered for other Apicomplexan parasites such as Babesia sp. or Plasmodium sp.
