Abstract In this study, we report for the first time the successful infestation of rabbits with just-molted, unfed adults of Rhipicephalus microplus. Six New Zealand White rabbits were experimentally infested with 20 female and 20 male unfed adult ticks released into plastic chambers fixed on the shaved backs of each host. The attachment and feeding processes were successful. The biological characteristics of the ticks and the occurrence of adverse events in the tick-attachment area were studied. The average engorgement period was 10.7 days, and 33.3% of the engorged females completed the parasitic phase. The average weight of the recovered engorged females was 149.8 mg, with an average egg mass weight of 70.9 mg, a conversion efficiency index of 47.3%, and a hatching percentage of 88.31%. The adverse reactions found in the tick-attachment area were the usual inflammatory responses of the organism to infestation by these ectoparasites; however, it did not prevent the ticks from feeding and completing their life cycle. These data indicate that the infestation of rabbits with just-molted, unfed adult ticks could be a valuable, alternative animal model for rapid and economical evaluation of vaccine candidates and new molecules with acaricidal activity against Rhipicephalus microplus.

Resumo Neste estudo, relata-se, pela primeira vez, o sucesso da infestação de coelhos por carrapatos adultos recém-mudados e não alimentados. Seis coelhos brancos da Nova Zelândia foram infestados artificialmente com 20 carrapatos adultos fêmeas e 20 machos adultos não alimentados no interior de câmaras de plástico fixadas no dorso de cada hospedeiro. Os processos de fixação e alimentação dos carrapatos foram bem sucedidos. Foram estudadas as características biológicas dos carrapatos e a ocorrência de eventos adversos na área de fixação do ectoparasito. O período médio de ingurgitamento foi de 10,7 dias, e 33,3% das fêmeas ingurgitadas completaram a fase parasitária. O peso médio das fêmeas ingurgitadas recuperadas foi de 149,8 mg, com peso médio da massa de ovos de 70,9 mg, índice de produção de ovos de 47,3% e porcentagem de incubação de 88,31%. Uma resposta inflamatória usual do organismo à infestação por esses ectoparasitas foi a única reação adversa encontrada na área de fixação dos carrapatos, o que não impediu que eles se alimentassem e completassem seu ciclo de vida. Esses dados apontam que a infestação de coelhos com carrapatos adultos recém-mudados e não alimentados pode ser um modelo animal alternativo e útil para a avaliação rápida e econômica de candidatos a vacinas e novas moléculas com atividade acaricida contra Rhipicephalus microplus.

ABSTRACT Introduction. Porvac( is a subunit vaccine against Classical Swine Fever (CSF), whose active principle is the chimeric protein between the E2 antigen and the molecular adjuvant CD154. Its ability to prevent transplacental transmission and to protect 7 days after one dose was demonstrated. This paper summarizes the safety, immunogenicity and efficacy studies of this vaccine at different ages and handling conditions. Methods. The vaccine was produced under GMP conditions. Dubroc x Yorkshire crossbreed swine were used in all experiments. The general immunization schedule consists in two immunizations on days 0 and 21 by the intramuscular route in the neck. The neutralizing antibody response was measured by the NPLA assay. Viral challenge experiments were conducted in controlled areas. Results and Discussion. Porvac( was safe and well tolerated in piglets and pregnant sows. No local or systemic reactions were documented. The number of offspring, their weight and survival in vaccinated sows was similar to unvaccinated controls. Different immunization schedules with Porvac( induce protective neutralizing antibodies (NAb). The titers of maternal derived antibodies (MDA) in the offspring of Porvac( or Attenuated Life vaccine and Porvac( vaccinated sows were higher than 1:200 up to at least 8 weeks of life. The MDA were able to protect piglets from a lethal viral challenge. Those MDA did not interfere with Porvac( vaccination of the piglets 15 days after birth or more. Finally, Porvac( induced NAb titers persisted during 9 months above 1:2000 and were still protective against the viral challenge. Conclusions. The results demonstrate the capacity of Porvac( to be safe and to induce robust and long term immunity through all the life of the animals, without immunological windows.

RESUMEN Introducción. Porvac( es una vacuna de subunidad contra la peste porcina clásica, cuyo principio activo es la proteína quimérica entre el antígeno E2 y el adyuvante molecular CD154. Se ha demostrado su capacidad para evitar la transmisión transplacentaria y proteger 7 días después de una dosis. El presente trabajo ha resumido los estudios de seguridad y eficacia de esta vacuna en diferentes edades y condiciones de manejo. Métodos. La vacuna se produjo en condiciones de BPM. Para los ensayos clínicos se emplearon cerdos Dubroc x Yorkshire. Por lo general, se empleó un esquema de 2 dosis los días 0 y 21 y se administraron 2 mL por vía intramuscular. La respuesta de anticuerpos neutralizantes se midió por NPLA. Los ensayos de desafío viral se realizaron en áreas controladas. Resultados. Se demostró la seguridad de Porvac( en crías y en cerdas gestantes. No se observaron reacciones locales ni sistémicas. El número de crías, su peso y sobrevida fue similar en las cerdas vacunadas y sus controles. Se evidenció la capacidad de Porvac( al inducir títulos de anticuerpos neutralizantes (AcN) protectores con diferentes esquemas. Los títulos de AcN calostrales (AcNC) en las crías de madres vacunadas con Porvac® o con VVA y Porvac( fueron superiores a 1:200 hasta al menos 8 semanas. Los AcNC fueron suficientes para proteger a las crías frente al reto viral letal. Se demostró que los AcNC no interferían en la vacunación con Porvac( en crías a partir de 15 días de nacidas. Finamente, los títulos de AcN inducidos por Porvac( persistieron durante 9 meses por encima de 1:2000 y protegieron frente al retoviral. Conclusiones . Los resultados evidenciaron la seguridad de Porvac( y su capacidad para inducir una inmunidad robusta y sostenida en los animales desde su nacimiento hasta la muerte, sin ventanas inmunológicas durante todo el ciclo productivo.