Protection of Dairy Cows Immunized with Tick Tissues against Natural Boophilus microplus Infestations in Thailand

Abstract

Boophilus microplus has a major impact on cattle production, and an antitick vaccine would be a valuable tool for control of this important ectoparasite in Thailand. Previous work has shown that immunization of hosts with different tick tissues has different implications regarding tick feeding and fecundity under experimental conditions. The purpose of this study was to assess the effects of immunization of dairy cattle with B. microplus salivary gland or midgut extracts on natural infestations by this tick species. The different antigen extracts (1 mg total protein) or equivalent amounts of adjuvant alone were injected intradermally every two weeks for a total of three times before allowing cattle to graze in a tick-contaminated pasture. Animals were checked daily, and engorged female ticks collected, counted, weighed, and maintained in tick incubators to observe tick performance parameters, including engorged weight, egg mass weight, nonviable eggs, mortality, oviposition period, egg incubation period, and F1 larval weight. After six months, each group was reimmunized with the same antigen and/or adjuvant, and ticks were again collected and evaluated. Immunization of cattle with salivary gland preparations resulted in reductions in mean tick counts and in engorged female weights. Immunization with midgut antigens reduced tick oviposition and reduced egg mass weights. In addition, more ticks recovered from midgut-immunized cows produce nonviable eggs. This investigation indicates that a vaccine based on these antigen preparations could induce a lasting, protective immune response against B. microplus that would be expected to provide a safe nontoxic means of tick control.

Molecular Analysis of Calreticulin Expressed in Salivary Glands of Rhipicephalus (Boophilus) microplus Indigenous to Thailand

“…R. microplus ticks were collected from cattle throughout Thailand. Dissection of ticks was done as previously described 2 . The salivary glands were separated from the rest of the organs and transferred into RNA stabilizer reagent, and kept frozen at −80°C until use.…”

Immunization with Tick Salivary Gland Extracts

“…Vaccination with concealed tick antigens is an alternative approach to tick control. Most reports on tick vaccine candidate antigens were concentrated on gross changes among ticks, such as weight or fecundity 1 . However, immunization of cattle with tick salivary gland extract (TSGE) was recently also associated with reduced incidence of tick‐borne disease among naturally infested cattle 2 .…”

Immune Response ofBos indicusCattle against the Anti-Tick Antigen Bm91 Derived from LocalRhipicephalus (Boophilus) microplusTicks and Its Effect on Tick Reproduction under Natural Infestation

“…The high variation of tick counts between animals indicates the skewed distribution of ticks in a herd as shown previously [18]. The study of Jittapalapong et al [48] was conducted under comparable conditions. Nevertheless, the tick infestation was considerably higher.…”

“…Generally, the natural tick infestation in field experiments varies depending on a variety of factors, mainly climatic, and is difficult to predict [14, 49]. The primary immunization was immediately given before the onset of the rainy season; however, the tick infestation during the following rainy season was lower compared to other studies with natural infestation [48]. …”