Selective versus strategic control against Rhipicephalus microplus in cattle: A comparative analysis of efficacy, animal health, productivity, cost, and resistance management.

This study compared selective control versus strategic control against Rhipicephalus (Boophilus) microplus, under conditions of a real dairy farm. Strategic control requires that all animals be treated with acaricide at regular pre-determined intervals. Selective control only requires treatment of infested animals and only when they are at or above a pre-determined threshold. Tick counts on animals and in pasture were performed and the susceptibility of tick populations to the different treatment methods was evaluated at the beginning and end of the study using the Larval Packet Test, Larval Immersion Test, and Adult Immersion Test. Over the four years of the study strategic control was more advantageous than the selective control as the group experienced lower tick burden on animals and in pasture, absence of skin lesions and myiases, lower operating costs, treatments concentrated in fewer months of the year and lower resistance pressure.

First description of conspecific hyperparasitism in Amblyomma sculptum.

The present study reports a case of conspecific hyperparasitism for Amblyomma sculptum. Two partially engorged females were collected from two naturally infested dairy cows and placed in a single petri dish to be transported to the laboratory, where they were held in a biological oxygen demand (BOD) incubator chamber under controlled conditions of 27 ± 1 °C and 85 ± 5% RH. After one day, it was observed that the smaller female (female 1) was attached to the dorsal surface of the larger female (female 2). The hypostome and chelicerae of the female 1 were entirely inserted into the cuticle of the female 2, characterizing tick attachment. Pictures were taken to illustrate the finding. After a few hours, the female 1 detached spontaneously and showed no visible signs of additional enlargement (engorgement). The females did not lay eggs and the survival period was not recorded. To our knowledge this is the first report of hyperparasitism for A. sculptum and the fourth for the genus Amblyomma.

Population dynamics of Rhipicephalus microplus in dairy cattle: influence of the animal categories and correlation with milk production.

Is well known the taurine and zebuine susceptibility to Rhipicephalus microplus. Few are the reports regarding tick population dynamics between the same herd/breed, and because of this, two experiments were performed. In the 1st, the cattle tick population dynamics in dairy nursing calves (reared collective and individually), weaning calves (4-16 months), heifers (17-29 months), cows in lactation and dry cows (≥ 30 months) from the same herd, tick burden and milk production correlation were performed, for two years. R. microplus females (4.5-8.0 mm) counts and the milk production were performed every 28 and 14 days, respectively. In the 2nd experiment, bovines belonging to different categories/age (newborn without previous contact with tick; 12-13 months with tick contact since birth; and 23-24 months with tick contact since birth) were experimentally infested with 30,000 R. microplus larvae, to quantify the number of fully engorged females detached from these animals. In the 1st experiment, when the mean counts of tick were ≥ 30 all animals of the group were treated. Nursing calves showed 3-4 peaks of ticks, animals reared individually showed smaller (p ≤ 0.05) tick burden than those reared collectively. Weaning calves (4-8 months) showed 5 tick peaks/year and higher mean tick burden was found than other categories. On the other hand, animals with 17-29 months of age showed smallest (p ≤ 0.05) tick burden, with 3 tick peaks/year. When the animal become lactating the tick burden increase, and 5 peaks/year occurred, and decrease again in dry cows (p ≤ 0.05) showing 4-5 tick peaks/year. Weaning calves and lactating cows received more acaricide treatments (p ≤ 0.05), 18 and 15, respectively. Nursing calves reared individually, and heifers (21-29 months) were the categories that received two acaricide treatments. The more milk the cow produce, more ticks it has (p ≤ 0.05). In the 2nd experiment, more (p ≤ 0.05) fully engorged females were recovered from younger animals than older ones. So, different tick control strategies need to be adopted in different dairy cattle categories, and the tick burden should be considered, once the effect may be more inherent to the animal rather than the strategy adopted.

Rhipicephalus microplus: An overview of vaccine antigens against the cattle tick.

Rhipicephalus microplus, popularly known as the cattle tick, is the most important tick of livestock as it is responsible for significant economic losses. The use of chemical acaricides is still the most widely used control method despite its known disadvantages. Vaccination would be a safe alternative for the control of R. microplus and holds advantages over the use of chemical acaricides as it is environmental-friendly and leaves no residues in meat or milk. Two vaccines based on the Bm86 protein were commercialized, TickGARD® and Gavac®, with varying reported efficacies in different countries. The use of other vaccines, such as Tick Vac®, Go-Tick®, and Bovimune Ixovac® have been restricted to some countries. Several other proteins have been analyzed as possible antigens for more effective vaccines against R. microplus, including peptidases, serine proteinase inhibitors, glutathione S-transferases, metalloproteases, and ribosomal proteins, with efficacies ranging from 14% to 96%. Nonetheless, more research is needed to develop safe and efficient tick vaccines, such as the evaluation of the efficacy of antigens against other tick species to verify cross-reactivity and inclusion of additional antigens to promote the blocking of the infection and spreading of tick-borne diseases. This review summarizes the discoveries of candidate antigens for R. microplus tick vaccines as well as the methods used to test their efficacy.

Control of infective larvae of gastrointestinal nematodes in heifers using different isolates of nematophagous fungi.

The effect of different nematophagous fungi [Duddingtonia flagrans (AC001 and CG722) and Monacrosporium thaumasium (NF34)] with regard to controlling infective larvae (L3) of nematodes after gastrointestinal transit in female cattle (3/4 Holstein × Zebu) was evaluated. A total of 24 pubescent female cattle were used, weighing approximately 320 kg each one. There were three treatment groups, each contained six animals that received 150 g of pellets (0.2 g of mycelium), orally in a single dose, in a sodium alginate matrix containing mycelial mass of the fungus D. flagrans (AC001 or CG722) or M. thaumasium (NF34); and one control group (without fungi). Fecal samples were collected from the animals at intervals of 12, 15, 18, 21, 24, 48, and 72 hours. At the end of 17 days, the L3 not subjected to predation were recovered by means of the Baermann method. The fungal isolates tested were capable of destroying the L3 after gastrointestinal transit. It was observed that within 72 hours, the isolates AC001, CG722, and NF34 showed a higher predatory activity (81.2%, 97.3%, and 98.3%, respectively). The results justify the need for studies in the field, and over longer intervals, in order to observe the efficiency of the fungus D. flagrans, or even M. thaumasium, for environmental control over nematodes in naturally infected cattle.

Control of infective larvae of gastrointestinal nematodes in heifers using different isolates of nematophagous fungi / Controle de larvas infectantes de nematóides gastrintestinais de novilhas por diferentes isolados dos fungos nematófagos

The effect of different nematophagous fungi [Duddingtonia flagrans (AC001 and CG722) and Monacrosporium thaumasium (NF34)] with regard to controlling infective larvae (L3) of nematodes after gastrointestinal transit in female cattle (3/4 Holstein × Zebu) was evaluated. A total of 24 pubescent female cattle were used, weighing approximately 320 kg each one. There were three treatment groups, each contained six animals that received 150 g of pellets (0.2 g of mycelium), orally in a single dose, in a sodium alginate matrix containing mycelial mass of the fungus D. flagrans (AC001 or CG722) or M. thaumasium (NF34); and one control group (without fungi). Fecal samples were collected from the animals at intervals of 12, 15, 18, 21, 24, 48, and 72 hours. At the end of 17 days, the L3 not subjected to predation were recovered by means of the Baermann method. The fungal isolates tested were capable of destroying the L3 after gastrointestinal transit. It was observed that within 72 hours, the isolates AC001, CG722, and NF34 showed a higher predatory activity (81.2%, 97.3%, and 98.3%, respectively). The results justify the need for studies in the field, and over longer intervals, in order to observe the efficiency of the fungus D. flagrans, or even M. thaumasium, for environmental control over nematodes in naturally infected cattle.

No presente estudo, foi avaliado o efeito de diferentes fungos nematófagos [Duddingtonia flagrans (AC001 e CG722) eMonacrosporium thaumasium (NF34)] no controle de larvas infectantes (L3) de nematóides após o trânsito gastrointestinal em fêmeas bovinas (3/4 Holandês x Zebu). Um total de 24 fêmeas bovinas pubescentes foram utilizadas, pesando aproximadamente 320 kg cada. Foram utilizados três grupos de tratamento; cada um contendo seis animais que receberam por via oral de 150 g de péletes (0,2 g de micélio), em dose única, em uma matriz de alginato de sódio contendo massa micelial dos fungos D. flagrans (AC001 ou CG722), M. thaumasium (NF34), além de um grupo controle (sem fungo). Amostras de fezes foram colhidas dos animais em intervalos de 12, 15, 18, 21, 24, 48 e 72 horas. No final de 17 dias, as L3 não predadas foram recuperadas pelo método de Baermann. Os isolados de fungos testados foram capazes de destruir as L3 após trânsito gastrointestinal. Observou-se após 72 horas, os isolados AC001, CG722 e NF34 mostraram uma maior atividade predatória (81,2%, 97,3% e 98,3%, respectivamente). Estes resultados justificam a necessidade de estudos a campo e em intervalos mais longos, a fim de observar a eficácia dos fungos D. flagrans ou mesmoM. thaumasium no controle ambiental dos nematóides de bovinos naturalmente infectados.

PCR em tempo real para diagnóstico da leucose enzoótica bovina / Enzootic bovine leukosis real time PCR

O objetivo deste trabalho foi realizar a validação de uma reação em cadeia da polimerase em tempo real com o sistema Plexor® (qPCR) para o diagnóstico da Leucose Enzoótica Bovina (LEB), por meio da comparação com testes de diagnóstico recomendados pela Organização Mundial de Saúde Animal (OIE). A qPCR foi comparada com duas outras técnicas: a PCR nested (nPCR) e a imunodifusão em gel de ágar (IDGA). Das 82 amostras analisadas pela qPCR e nPCR, 79 apresentaram resultados concordantes, sendo a concordância, classificada pelo Índice Kappa, como alta. Entre as PCRs e a IDGA, o número de resultados concordantes foi de 71 e 69, respectivamente, para qPCR e nPCR, sendo a concordância classificada como considerável. A qPCR apresentou altos valores de sensibilidade e especificidade. Os valores preditivos da qPCR observados demonstraram a alta capacidade de classificação dos casos positivos e negativos. A qPCR não foi capaz de detectar três amostras positivas e tem custo ligeiramente superior que a nPCR. Entretanto, a qPCR é uma técnica mais rápida, menos susceptível a contaminações, tem alta sensibilidade, não utiliza e não gera resíduos carcinogênicos. Concluímos que a qPCR pode substituir a nPCR recomendada pela OIE no diagnóstico de rotina em áreas em que a LEB é endêmica, como no Brasil.

The goal of this research was to validate a Plexor® real time Polymerase Chain Reaction (qPCR) for Enzootic Bovine Leukosis (EBL) diagnosis by comparison with methods recommend by the World Animal Health Organization (OIE). The qPCR was compared with two other techniques: the nested PCR (nPCR) and to the agar gel immunodiffusion (AGID). Of 82 qPCR and nPCR analysed samples, 79 presented concordant results, being the concordance classified by Kappa Index as high. Between the PCRs and AGID, the number of concordant results was 71 and 69, out of 82, to qPCR and nPCR, respectively, being the concordance classified as considerable, in both cases. The qPCR presented high specificity and sensitivity values. The observed qPCR negative and positive predictive values show that the qPCR has a high capacity to correctly classify positive and negative results. The qPCR was not able to detect three positive animals and has a lightly higher cost than the nPCR. However, the qPCR its faster, less prone to contamination, has a high sensitivity and does not use or generate carcinogenic residues. We conclude that the qPCR may be used to replace the OIE nPCR technique in routine diagnosis in areas where EBL is endemic, as is the case of Brazil.

Amblyomma rotundatum (Koch, 1844) (Acari: Ixodidae) two-host life-cycle on Viperidae snakes.

Amblyomma rotundatum is an ixodid tick that infests ectothermic animals and reproduces exclusively by parthenogenesis. This tick has been frequently reported to infest reptiles and amphibians, under natural conditions and sometimes in captivity. It was described in Brazil and several other countries of South, Central and North America. Although many studies have reported aspects of its biology, none of them has used regularly either ophidian as hosts, or controlled temperature, humidity and luminosity for parasitic stages. The objective of this experiment was to study the life cycle of A. rotundatum feeding on Viperidae snakes under room controlled conditions at 27 ± 1 °C temperature, 85 ± 10% relative humidity and 12:12 hours photoperiod for parasitic stages, and under B.O.D incubator conditions at 27 ± 1 °C temperature, 85 ± 10% relative humidity and scotophase for non-parasitic stages. The total duration of the life cycle ranged from 56 to 163 days (mean of 105 days). Two-host life cycle was observed for most of the ixodid population studied.

Amblyomma rotundatum (Koch, 1844) (Acari: Ixodidae) two-host life-cycle on Viperidae snakes / Ciclo dioxênico em Amblyomma rotundatum (Koch, 1844) (Acari: Ixodidae)parasitando serpentes da família Viperidae

Amblyomma rotundatum is an ixodid tick that infests ectothermic animals and reproduces exclusively by parthenogenesis. This tick has been frequently reported to infest reptiles and amphibians, under natural conditions and sometimes in captivity. It was described in Brazil and several other countries of South, Central and North America. Although many studies have reported aspects of its biology, none of them has used regularly either ophidian as hosts, or controlled temperature, humidity and luminosity for parasitic stages. The objective of this experiment was to study the life cycle of A. rotundatum feeding on Viperidae snakes under room controlled conditions at 27 ± 1 ºC temperature, 85 ± 10 percent relative humidity and 12:12 hours photoperiod for parasitic stages, and under B.O.D incubator conditions at 27 ± 1 ºC temperature, 85 ± 10 percent relative humidity and scotophase for non-parasitic stages. The total duration of the life cycle ranged from 56 to 163 days (mean of 105 days). Two-host life cycle was observed for most of the ixodid population studied.

Amblyomma rotundatum é um carrapato da família Ixodidae, parasito de animais pecilotérmicos, e que se reproduz exclusivamente por partenogênese. Este carrapato é frequentemente relatado infestando répteis e anfíbios em condições naturais e, às vezes, em animais de cativeiro. Ele já foi relatado no Brasil e em vários outros países das Américas do Sul, Central e do Norte. Embora muitos estudos sobre sua biologia tenham sido publicados, nunca foram utilizados ofídios como hospedeiros e, tão pouco, foram realizados ensaios com os estádios parasitários sob condições controladas de temperatura, umidade e iluminação. O objetivo deste experimento foi estudar o ciclo biológico de A. rotundatum se alimentando em serpentes da família Viperidae sob condições ambientais controladas a 27 ± 1 ºC de temperatura, 85 ± 10 por cento de umidade relativa do ar e 12:12 horas de fotoperíodo para estágios parasitários; assim como sob condições iguais a 27 ± 1 ºC de temperatura, 85 ± 10 por cento de umidade relativa do ar e escotofase em estufas de germinação para estádios não parasitários. A duração total do ciclo de vida variou de 56 a 163 dias (média de 105 dias). Observou-se ciclo dioxênico para a a maior parte da população dos ixodídeos em estudo.

Biology of Amblyomma aureolatum (Pallas, 1772) (Acari: Ixodidae) on some laboratory hosts in Brazil

The ixodid Amblyomma aureolatum is suspected to play a role in the epidemiology of wild life-cycle hemoparasites, which frequently infect dogs in rural and hunting areas in Brazil. Little is known about its bionomics. The objective of the present study was to evaluate some bionomic aspects of A. aureolatum ticks in Brazil. One engorged female, collected from a dog (Canis familiaris) in Säo Sebastiäo das Aguas Claras, State of Minas Gerais, was used to establish a colony in the laboratory. Subsequently its parasitic stage progeny were fed on domestic dogs and laboratory animals. The free-living stages were incubated at 27ºC ± 2°C and minimum 70 percent relative humidity in a BOD incubator. The egg incubation period ranged from 31 to 34 days; the parasitic period of larvae ranged from 4 to 6 days and ecdysis to nymphs occurred from day 19 up to day 22. The parasitic period of nymphs ranged from 5 to 8 days and the period of ecdysis to adults from 31 to 33 days. The parasitic period of adults ranged from 11 to 15 days, the pre-oviposition period from 6 to 12 days, and the oviposition period from 9 to 38 days. The total duration of the life cycle ranged from 116 to 168 days