Fernanda Silva Fortes

Challenges of nematode control in ruminants: Focus on Latin America

Gastrointestinal nematodes (GIN) of ruminants (cattle, sheep and goats) are ubiquitous and can cause severe injuries to infected animals and significant losses in farming revenues. GIN are able to survive severe environmental and host conditions, but mankind has developed a number of ingenious methods for parasite control. The commerce and use of modern anthelmintic drugs with a broad spectrum of activity has been a solid tool for nearly 40 years, however the continuous use of these drugs, has led to the selection of populations of drug-resistant worms worldwide. At present, the ever-growing agricultural systems in Latin America are facing many challenges and cannot rely on the far-reaching objective of parasitic elimination from the host or the environment. The lack of extensive programs for monitoring drug resistance exacerbates the negative consequences of reduced efficacy, which is evident in some areas with the increase in mortality rate even after treatment. Experts agree that new schemes of parasitic control are needed and should be based on the strategy of targeted selective treatment where affected hosts are identified and treated accordingly. In this article, we will focus our discussion on the challenges for the control of GIN in Latin America by 2020 imposed by reduced drug efficacy. We will evaluate phenotypic and molecular markers, methods for single-animal evaluation, and the implementation of schemes for anthelmintic treatment that address parasites in refugia.

Mapping risk of bovine fasciolosis in the south of Brazil using Geographic Information Systems.

Fasciolosis, caused by Fasciola hepatica, is an endemic disease of ruminants that occurs in several countries of South America where it can lead to decreased production and fertility and, in severe cases, animal death. Although very prevalent, information on the epidemiology of the disease is incomplete in Brazil. The objective of the present study was to define the prevalence of F. hepatica in the livers of cattle from slaughterhouses and correlate the data with the animals origin (climate and altitude) using a Geographic Information System (GIS). The data was used to create an epidemiological map of fasciolosis by state (Rio Grande do Sul, Santa Catarina, Paraná), by municipality (n=530) and by year (2003-2008). Information was analyzed using a databank from slaughterhouses with Federal Inspection Services of the Ministry of Agriculture. The highest cattle infection rate was found in the two most Southern states of Rio Grande do Sul (18.7%) and Santa Catarina (10.1%). Animals from the Campanha region of Rio Grande do Sul and from the central coast area of Santa Catarina had prevalences of greater than 40%. Cattle from low altitudes municipalities were significantly more likely to have the disease (p<0.05). No significant differences were found between high or low prevalence and ambient temperatures. Risk maps resulting from this study provide information on the epidemiology and transmission of F. hepatica in Southern Brazil needed for design of appropriate control measures to control economic impacts. F. hepatica may represent an important source of zoonotic infection of humans as well; therefore these findings may be complemented by future studies on human infections in high risk areas.

Resistência anti-helmíntica em nematoides gastrintestinais de pequenos ruminantes: avanços e limitações para seu diagnóstico

Fortes F.S. & Molento M.B. 2013. (Anthelmintic resistance in gastrointes- tinal nematodes of small ruminants: advances and limitations for diagnosis.) Resis- tencia anti-helmintica em nematoides gastrintestinais de pequenos ruminantes: avancos e limitacoes para seu diagnostico. Pesquisa Veterinaria Brasileira 33(12):1391-1402. Labora- torio de Doencas Parasitarias, Universidade Federal do Parana, Rua dos Funcionarios 1540, Curitiba, PR 80035-050, Brazil. E-mail: fortesfs@gmail.com The selection and growing spread of resistant nematodes to the most commonly used anthelmintics, benzimidazoles (BZs), imidazoles and macrocyclic lactones (MLs), constitu- tes a serious obstacle of small ruminants production worldwide. The use of efficient and sensitive methods for detection and monitoring of anthelmintic resistance in the field beco- mes urgent, especially for the BZs and MLs groups due to its frequent resistant reports. Ob- taining an early and accurate diagnosis of resistance is extremely important to aid decision- -making regarding parasite control programs, with the objective to preserve the lifespan of existing products, and to limit the development of resistance in nematode populations. The in vivo tests and the more recent in vitro tests have been developed for the detection of ne- matode resistant to the major anthelmintic groups. However, the availability of validated in vitro tests and its practical use is still very limited. Although the faecal egg-count reduction test (FECRT, in vivo - indirect) is the primary method of choice for the detection of resistan- ce in the field it has being criticized for its results and is receiving significant modifications. Moreover, the development of molecular techniques from genomic changes have generated considerable advances in this research area, with the use of mutations at codons 167, 198 and 200 of β-tubulin gene as the main SNPs (single nucleotide polymorphisms) associated with BZs resistance. This review aims to discuss the available diagnostic methods for the detection of anthelmintic resistance in nematodes of small ruminants, highlighting key de- velopments and obstacles to its use in the laboratory and in the field.

Serological survey of Rickettsia sp. in horses and dogs in an non-endemic area in Brazil

Brazilian Spotted Fever (BSF) is a lethal rickettsiosis in humans caused by the bacteria Rickettsia rickettsii, and is endemic in some areas of Brazil. Horses and dogs are part of the diseases life cycle and they may also serve as sentinel animals in epidemiological studies. The first human BSF case in the State of Paraná was reported in 2005. The present study was conducted in the municipality of Almirante Tamandaré, where no previous case of BSF was reported. Serum samples were collected from 71 horses and 20 dogs from nine properties in the area. Ticks were also collected from these animals. All farmers completed a questionnaire about their knowledge of BSF and animal health management. Serum samples were analyzed by indirect immunofluorescent-antibody assay (IFA) using R. rickettsii and R. parkeri as antigens. Ticks were analyzed by PCR for Rickettsia sp., and all of them were PCR-negative. Six horses (8.45%) and 4 dogs (20%) were identified as seropositive. Farmers were not aware of the correlation between the presence of ticks and risk of BSF. Although a non-endemic area, Almirante Tamandaré is a vulnerable environment for BSF and effective tick control measures are required.

Partial selective treatment of Rhipicephalus microplus and breed resistance variation in beef cows in Rio Grande do Sul, Brazil.

Rhipicephalus microplus infestation causes heavy losses in cattle. The majority of farmers control the cattle tick by using long-acting drugs throughout the year, which evidently increases selection pressure for drug resistance. Partial selective treatment (PST) may be used to directly reduce selection pressure by treating only the portion of the herd that is most infested. The objective of this work was to determine the effect of PST in two herds of beef cows and the effect of breed tolerance. The Santiago (n=306 animals) and the São Francisco de Assis (n=204 animals) herds were composed of up to eight pure breeds of Bos taurus and Bos indicus and their crosses and were evaluated during the first and second (8 months) tick generations. Ticks larger than 4.5mm were counted on one side of the animal, and the animals were treated when numbers exceeded 20 ticks per host. On both farms, the tick-tolerant breeds with a high proportion of B. indicus (Braford, Brangus, and Nellore) consistently carried fewer ticks than Charolais. The economical evaluation showed an average profit margin in the use of PST of 674.25% and 1394.5% on the Santiago and São Francisco de Assis farms, respectively, in comparison to all-herd treatment. These results indicate that PST is a reliable tool for health management and may be used as a standard protocol for tick control with significant economic benefits on farms. In addition, the maintenance of the highest possible tolerant/resilient breeds is also an essential factor that should be considered in todays more sustainable animal production systems.

Seroprevalence of Rickettsia bellii and Rickettsia felis in dogs, São José dos Pinhais, State of Paraná, Brazil.

Brazilian spotted fever (BSF) is a vector-borne zoonosis caused by Rickettsia rickettsii bacteria. Dogs can be host sentinels for this bacterium. The aim of the study was to determine the presence of antibodies against Rickettsia spp. in dogs from the city of São José dos Pinhais, State of Paraná, Southern Brazil, where a human case of BSF was first reported in the state. Between February 2006 and July 2007, serum samples from 364 dogs were collected and tested at 1:64 dilutions by indirect immunofluorescence assay (IFA) against R. rickettsii and R. parkeri. All sera that reacted at least to one of Rickettsia species were tested against the six main Rickettsia species identified in Brazil: R. rickettsii, R. parkeri, R. bellii, R. rhipicephali, R. amblyommii and R. felis. Sixteen samples (4.4%) reacted to at least one Rickettsia species. Among positive animals, two dogs (15.5%) showed suggestive titers for R. bellii exposure. One sample had a homologous reaction to R. felis, a confirmed human pathogen. Although Rickettsia spp. circulation in dogs in the area studied may be considered at low prevalence, suggesting low risk of human infection, the present data demonstrate for the first time the exposure of dogs to R. bellii and R. felis in Southern Brazil.

Evaluation of resistance in a selected field strain of Haemonchus contortus to ivermectin and moxidectin using the Larval Migration on Agar Test

Haemonchus contortus e uma das causas mais comuns e economicamente significativas de doenca em producoes de pequenos ruminantes em todo o mundo, e os programas de controle de parasitas nematoides - incluindo H. contortus - baseiam-se principalmente no uso de drogas anti-helminticas. A consequencia da utilizacao desses compostos, como sendo a unica estrategia sanitaria para evitar infeccoes por parasitas, tem sido a reducao da eficacia de todos os produtos quimioterapicos, selecionando fortemente para resistencia. O desenvolvimento generalizado da resistencia anti-helmintica e a dificuldade de seu diagnostico precoce tem sido uma grande preocupacao para o manejo sustentavel de parasitas no campo. O objetivo desta pesquisa foi determinar e comparar o efeito da ivermectina (IVM) e da moxidectina (MOX) em um isolado de campo selecionado de H. contortus com um estado de resistencia conhecido, utilizando o teste in vitro de migracao de larvas em agar (LMTA). Larvas de terceiro estagio de um isolado de H. contortus selecionado foram obtidas a partir de culturas de fezes de ovinos infectados experimentalmente e incubadas em onze concentracoes diluidas crescentes de IVM e MOX (6, 12, 24, 48, 96, 192, 384, 768, 1536, 3072 e 6144µg/mL). As curvas sigmoides de dose-resposta foram obtidas utilizando o valor de R2 >0,90 e a dose de concentracao letal (CL50) para as drogas anti-helminticas testadas, utilizando um modelo logistico de quatro parâmetros. O valor de CL50 para MOX foi significativamente menor do que para IVM (1,253µg/mL e 91,06µg/mL), identificando o isolado de H. contortus como consideravelmente menos suscetivel a IVM em comparacao a MOX. Alem disso, o LMTA mostrou uma alta consistencia (p<0,0001) e pode ser uma ferramenta util de diagnostico para monitorar o status de resistencia de IVM e MOX em isolado de campo de H. contortus, assim como ser utilizado de forma oficial e em rotina para programas de monitoramento das drogas sob a demanda do Ministerio da Agricultura (MAPA).