Argasid Tick Species Research Articles

Antibody Responses of Laboratory Mice to Sequential Feedings by Two Species of Argasid Ticks (Acari: Argasidae)

The host antibody response of CD1 mice resulting from sequential exposures to two species of Ornithodoros ticks was isotyped (ELISA) in an effort to determine the mechanism for the development of acquired resistance. In addition, salivary gland proteins from two argasid and one ixodid species were examined (RIA) for cross-reactivity. Significant antibody responses, detectable for at least 90 d after last exposure, were shown to occur. Isotyping showed that the initial response was of the IgM class with a secondary class switch to the IgG1 subclass occurring. Evidence that cross-reactive proteins exist between argasid and ixodid ticks is also discussed.

Experimental Studies on the Replication and Transmission of Crimean-Congo Hemorrhagic Fever Virus in some African Tick Species

Seven African tick species were studied as potential vectors of Crimean-Congo hemorrhagic fever (CCHF) virus. Engorged nymphae of 4 ixodid species, Hyalomma marginatum rufipes, H. truncatum, Rhipicephalus evertsi mimeticus, and Amblyomma hebraeum, were inoculated intracoelomically with CCHF virus and assayed for virus content at varying times post-inoculation. The virus replicated in all 4 species, reaching maximum titers of 4.6-5.5(10) fluorescence focus units per ml on days 5-9 post-inoculation. Virus titers declined up to the molt, but increased slightly on emergence of adult ticks. Thereafter, virus titers declined progressively, but infectivity could still be detected in adult ticks for up to 205 days post-inoculation. Groups of H. m. rufipes, H. truncatum, and R.e. mimeticus infected adults were fed on susceptible sheep and successfully transmitted CCHF infection. CCHF virus was not isolated from pools of the larval and nymphal progeny of the female ticks nor did the larvae transmit infection to guinea pigs by bite. CCHF virus failed to replicate in adults and nymphae of 3 argasid tick species, Argas walkerae, Ornithodorus porcinus porcinus, and O. savignyi, after intracoelomic inoculation and could be reisolated from the ticks no later than 1 day post-inoculation. The results suggest that all ixodid ticks are capable of transmitting CCHF virus but argasid ticks do not appear to be capable of serving as vectors.

Electrophoretic Analysis of the Ticks Ornithodoros (Pavlovskyella) Erraticus and O. (P.) Sonrai (Acari: Argasidae)1

Horizontal starch gel electrophoresis was used to examine the isozyme profiles of 2 argasid tick species, Ornithodoros erraticus and Ornithodoros sonrai . Of the 9 loci examined, malate dehydrogenase ( Mdh ), hexokinase ( Hk ), and phosphoglucomutase ( Pgm ) proved to be species-diagnostic, showing no genetic overlap. The technique provides a means of monitoring colonies of the 2 species to check for cross-contamination and also clarifies the taxonomic status of the 2 forms.

Autogeny in the tick Ornithodoros tholozani (Ixodoidea, Argasidae).

Autogeny is described as a characteristic (but variable) feature in certain species of argasid ticks. In Ornithodoros tholozani, females which are relatively large at ecdysis are autogenous, and smaller ones are not. The smallest females did not attract males before feeding. A positive correlation was found between the weight of the female at ecdysis and the number of eggs in the first autogenous oviposition. The percentage egg hatch was variable but an average of 57% of eggs from autogenous females hatched compared with 85–90% from anautogenous females. The duration of the preoviposition period and its possible relationship to the development of oocytes arc discussed.