Vaccination of feral pigs (Sus scrofa) using iophenoxic acid as a simulated vaccine

Iophenoxic acid derivatives as markers of oral baits to wildlife. New tools for their detection in tissues of a game species and safety considerations for human exposure

The bait-marker iophenoxic acid (IPA) and its derivatives are increasingly used for evaluating and optimizing the cost-effectiveness of baiting campaigns on wildlife, particularly on game species such as the wild boar. We aimed to determine whether concentrations of the three main IPA derivatives ethyl, methyl and propyl-IPA measured on thoracic liquid extracts (TLE) of hunted wild boars may be representative of two exposure doses, 40 and 200 mg, from 20 to 217 days after ingestion. Then we developed a method of detection of the three IPA derivatives by LC/ESI-MS-MS in muscle and liver to evaluate the suitability of these two other tissues for monitoring the marked bait consumption and for measuring available residues in the meat of marked animals. Three semi-captive wild boars received 40 mg of each IPA derivative, three received 200 mg, and three, as controls, did not receive IPA. Blood serum was sampled 20, 197 or 217 days after IPA exposure according to animals and to the derivative. Wild boars were shot by gun after the different times of serum sampling times, and TLE, muscle and liver were sampled. Our results suggest that TLE is not a relevant tissue for quantitatively expressing IPA exposure. Due to interference, no analytical method was validated on TLE containing digestive material. On the other hand, quantifications in the muscle and particularly in the liver could discriminate wild boars that had ingested the two IPA doses from 20 days until 7 months after exposure, especially for the two long term markers ethyl and propyl-IPA. So IPA quantifications in the liver sampled on hunted animals appear to be a reliable tool for monitoring bait consumption in the field at a large scale. Nevertheless, whatever the ingested dose, ethyl- and propyl-IPA concentrations measured in the muscle and the liver of tested animals until 217 days after exposure, remained higher than 0.01 mg/kg, the Maximal Residue Limit (MRL) is recommended for molecules for which no toxicological data are available. Based on the range of IPA residues available in these two tissues, implications for humans consuming marked animals are discussed.

Progress in Oral Vaccination against Tuberculosis in Its Main Wildlife Reservoir in Iberia, the Eurasian Wild Boar

Eurasian wild boar (Sus scrofa) is the main wildlife reservoir for tuberculosis (TB) in Iberia. This review summarizes the current knowledge on wild boar vaccination including aspects of bait design, delivery and field deployment success; wild boar response to vaccination with Bacillus Calmette-Guérin (BCG) and inactivated Mycobacterium bovis; and wild boar vaccination biosafety issues as well as prospects on future research. Oral vaccination with BCG in captive wild boar has shown to be safe with significant levels of protection against challenge with virulent M. bovis. An oral vaccination with a new heat-killed M. bovis vaccine conferred a protection similar to BCG. The study of host-pathogen interactions identified biomarkers of resistance/susceptibility to tuberculosis in wild boar such as complement component 3 (C3) and methylmalonyl coenzyme A mutase (MUT) that were used for vaccine development. Finally, specific delivery systems were developed for bait-containing vaccines to target different age groups. Ongoing research includes laboratory experiments combining live and heat-killed vaccines and the first field trial for TB control in wild boar.

Acceptance and palatability for domestic and wildlife hosts of baits designed to deliver a tuberculosis vaccine to wild boar piglets

Tuberculosis (TB) caused by Mycobacterium bovis, a member of the Mycobacterium tuberculosis complex, is an important health problem worldwide. The control of TB through vaccination of wildlife reservoirs may potentially have advantages over other management strategies. The most practical approach to deliver vaccines to wildlife is using oral baits that are stable under field conditions and effective in reaching the target species. Baits were developed in our laboratory to deliver oral vaccines to wild boar piglets. However, these baits were well accepted by other wild species. Therefore, bait consumption by different M. bovis hosts was evaluated herein. The results showed that the baits were well accepted by cattle, feral pigs, and adult red deer whereas small mammals like badgers and possums showed varying bait acceptance. Bait acceptance by different species has the advantage of targeting more than one wildlife reservoir when they coexist in the same area and need to be vaccinated for TB control. However, bait delivery methods such as the use of selective feeders to target the desired species should be developed to avoid bait consumption by other species.

A review of chemical, biological and fertility control options for the camel in Australia

Since their introduction to Australia in 1840 the one-humped camel, Camelus dromedarius, has gone from the colonist’s companion to a conservationist’s conundrum in the fragile arid ecosystems of Australia. Current management techniques are failing to curb present population growth and alternatives must be sought. This review assess the applicability of currently registered and developmental vertebrate pesticides and fertility control agents for camel control, as well as examining the potential usefulness of known C. dromedarius diseases for biological control. Not surprisingly, little is known about the lethality of most vertebrate pesticides used in Australia to camels. More has been published on adverse reactions to pharmaceuticals used in agriculture and the racing industry. An examination of the literature on C. dromedarius diseases, such as camel pox virus, contagious ecthyma and papillomatosis, indicates that the infections generally result in high morbidity but not necessarily mortality and this alone may not justify their consideration for use in Australia. The possibility exists that other undiscovered or unstudied biological control agents from other camilid species may offer greater potential for population control. As a long-lived species the camel is also not ideally suited to fertility control. Notwithstanding, anti-fertility agents may have their place in preventing the re-establishment of camel populations once they have been reduced through mechanical, biological or chemical means. Delivery of any generic chemical or fertility control agent will, however, require a species-tailored pathway and an appropriate large-scale deployment method. Accordingly, we put forward avenues of investigation to yield improved tools for camel control.

Selective piglet feeders improve age-related bait specificity and uptake rate in overabundant Eurasian wild boar populations

The Eurasian wild boar (Sus scrofa) is a reservoir for pathogens that affect both humans and domestic animals. The control of these diseases requires the development of strategies such as oral vaccination of the reservoir species. The aim of the present study was to determine the species-specific visitation and removal rates of cereal-based baits under field conditions in an overabundant wild boar population. Two different field trials were conducted at a hunting estate. In one trial, baits were placed at track stations set up either randomly in the undeveloped portions of the estate or close to permanent wild boar feeding places. In the second trial, baits were placed in feeders that were selective for use by wild boar piglets. Both trials were conducted in summer 2007 and repeated in spring 2008. No evidence of attractant effect by the bait was found when comparing baited against control stations. A close proximity to the feeders was associated with an increased probability of being visited by wild boar, and piglet feeders were shown to be highly selective for young wild boar. Baits disappeared faster in summer than in spring (i.e. ~70% consumption after the first day in selective feeders in summer, and 40% in spring). Therefore, a combination of a summer season and selective feeders was found to be a potentially reliable bait-deployment strategy for wild boar juveniles under Mediterranean conditions. These results support the use of selective feeders for oral delivery of baits to 2–4-month-old wild boar piglets, which is the preferred age for vaccination. Our delivery technique based on selective piglet feeders also has potential for other uses in the Eurasian wild boar and wild pigs under different management conditions.

Delivering and registering species-tailored oral antifertility products: a review

Technologies that induce infertility in wildlife are advancing rapidly. This is due largely to our increasing understanding of reproductive physiology, as well as the demand for management techniques that reduce fertility rather than increase mortality. However, transferring wildlife fertility control from the laboratory into landscape-scale utility for free-ranging animal populations will be highly dependent on products possessing oral activity and cost-effectiveness. A significant challenge to the delivery process is providing the international regulators in each jurisdiction with the most relevant data packages they need to assess new products. An essential part of any product registration for free-ranging animals will be the development of species-tailored delivery systems, especially so for non-specific antifertility actives. This review examines the current range of orally deliverable antifertility options, broadly classifies them according to overall risk compared with alternative vertebrate pesticides, outlines a species-tailoring process that reduces identified risks, and encompasses the data requirements for their registration for sale in Australasia, the USA and Europe.