Molecular method for the semiquantitative identification of gastrointestinal nematodes in domestic ruminants.

Standard diagnostic methods currently in use for the identification of helminth infections in ruminants are based on the morphological analysis of immature and adult stages of parasites. This paper describes a method for the semiquantitative identification of nematodes, mainly Trichostrongyloidea, at species-level resolution. The method is based on amplification and fragment analysis followed by minisequencing of the ITS-2 region (internal transcribed spacer 2) of the ribosomal DNA of parasite eggs or larvae. This method allows for the identification of seven genera (Chabertia, Cooperia, Haemonchus, Oesophagostomum, Ostertagia, Teladorsagia, and Trichostrongylus) and 12 species (Chabertia ovina, Cooperia curticei, Cooperia punctata, Cooperia oncophora/Cooperia surnabada, Haemonchus contortus, Haemonchus placei, Haemonchus longistipes, Oesophagostomum asperum, Oesophagostomum radiatum, Ostertagia ostertagi, Trichostrongylus axei, and Trichostrongylus colubriformis) of infectious nematodes of domestic ruminants. The concordance between the morphological and molecular analyses in the detection of genera ranged from 0.84 to 0.99, suggesting the proposed detection method is specific, semiquantitative, less laborious, and highly cost-efficient.

Bulk tank milk prevalence and production losses, spatial analysis, and predictive risk mapping of Ostertagia ostertagi infections in Mexican cattle herds.

This study investigated the prevalence, production losses, spatial clustering, and predictive risk mapping in different climate zones in five states of Mexico. The bulk tank milk samples obtained between January and April 2015 were analyzed for antibodies against Ostertagia ostertagi using the Svanovir ELISA. A total of 1204 farm owners or managers answered the questionnaire. The overall herd prevalence and mean optical density ratio (ODR) of parasite were 61.96% and 0.55, respectively. Overall, the production loss was approximately 0.542 kg of milk per parasited cow per day (mean ODR = 0.92, 142 farms, 11.79%). The spatial disease cluster analysis using SatScan software indicated that two high-risk clusters were observed. In the multivariable analysis, three models were tested for potential association with the ELISA results supported by climatic, environmental, and management factors. The final logistic regression model based on both climatic/environmental and management variables included the factors rainfall, elevation, land surface temperature (LST) day, and parasite control program that were significantly associated with an increased risk of infection. Geostatistical kriging was applied to generate a risk map for the presence of parasite in dairy cattle herds in Mexico. The results indicate that climatic and meteorological factors had a higher potential impact on the spatial distribution of O. ostertagi than the management factors.

First report of cattle farms with gastrointestinal nematodes resistant to levamisole in Mexico.

The objectives of the present study were: (1) to report the percentage of cattle farms with gastrointestinal nematodes (GINs) resistant to levamisole in Veracruz, Mexico, (2) to identify the genera of GINs involved in resistance, and (3) to identify factors associated with these resistances. The faecal egg count reduction test (McMaster technique) was used to detect the presence of resistant GINs. A questionnaire was given to owners to understand the history of anthelmintic use. The percentage of cattle farms with GINs resistant to levamisole was 36.4% (4/11). The percentage of faecal egg count reduction on resistant farms was 91%, 82%, 42% and 88%. A similar number of cattle farms (4/11) were identified as potentially having levamisole resistance. Only three farms had GIN populations susceptible to levamisole. Cooperia spp. was the genus most commonly found to be resistant, followed by Haemonchus spp., Ostertagia spp. and Oesophagostomum spp. No factors were identified that influenced the presence of GIN resistance. However, there were identified inappropriate anthelmintic practices in cattle farms that should be improved. None of the farmers weighed their animals in order to dose them correctly with anthelmintics. Six cattle farms (54.5%) applied anthelmintics to new arriving animals. This is the first report of levamisole resistant GINs in Mexico. Improving the use of anthelmintics and measures of quarantine for infected cattle will help control the spread of resistance.

Susceptibilidade à infecção por helmintos gastrintestinais em bovinos leiteiros da mesorregião do Sudoeste Paranaense, Brasil / Dairy cattle susceptibily to gastrointestinal helminth infection in the middle region of the southwest of Parana, Brazil / Susceptibilidad a la infección por helmintos gastrointestinales en bovinos lecheros de la mesoregión del Sudoeste Paranaense, Brasil

Foram avaliados os aspectos epidemiológicos e a dinâmica das infecções por helmintos gastrintestinais em bovinos da Mesorregião do Sudoeste Paranaense. Amostras de fezes de 473 bovinos criados em sistema extensivo foram coletadas para a contagem de ovos de nematódeos por grama de fezes (OPG). Coproculturas foram realizadas com as amostras que continham ovos para obtenção e identificação de larvas infectantes. Os resultados foram analisados pelos testes de Qui-quadrado ou Exato de Fischer. Detectou-se a prevalência dos gêneros Haemonchus, Cooperia, Trichostrongylus, Ostertagia e Oesophagostomum. As novilhas foram mais susceptíveis às infecções por nematodeos gastrintestinais em comparação com as vacas, sendo Haemonchus, Cooperia e Ostertagia os gêneros de parasitas mais prevalentes nestes animais.

Epidemiological aspects and dynamics of gastrointestinal helminthes were evaluated in cattle from Parana Southwest Region. Stool samples from 473 animals raised in extensive system were collected and analyzed for nematode eggs per gram faeces (EPG). Faecal cultures were made with samples that contained eggs in order to identify third stage larvae. The results were analyzed by Chi-square or Fischer exact tests. The following genera were found: Haemonchus, Cooperia, Trichostrongylus, Ostertagia and Oesophagostomum. The heifers were more susceptible to nematode gastrointestinal infections than the adult animals and Haemonchus, Cooperia and Ostertagia were the most common genera found in those animals.

Fueron evaluados los aspectos epidemiológicos y la dinamica de las infecciones por helmintos gastrointestinales de bovinos de la Mesoregión del Sudoeste Paranaense. Se tomaron muestras de heces de 473 bovinos criados bajo sistema extensivo para recuentos de huevos de nemátodos por gramo de heces (HPG). Se hicieron coprocultivos con las muestras que tenían huevos para obtención de larvas y su identificación. Los datos fueron analizados por medio del test Chi cuadrado o exacto de Fisher. Se detectó una prevalencia de los géneros Haemonchus, Cooperia, Trichostrongylus, Ostertagia y Oesophagostomum. La media de conteo de huevos según categoría de hembras fué mayor para las novillas que en vacas. Haemonchus, Cooperia y Ostertagia son los géneros de parasitos más prevalentes en estos animales.

Comparison of three methods for gastrointestinal nematode diagnosis determination in grazing dairy cattle in relation to milk production.

Development of resistance to anthelmintic drugs has motivated the search for diagnostic methods to identify animals for targeted selective treatments. We compared three methods for the diagnosis of nematode infection in relation to milk production in a fully grazing dairy herd of 150 cows in the humid Pampa (Argentina). Animals had feces, blood and milk sampled during the first postpartum month for EPG, pepsinogen and anti-Ostertagia antibody determination, respectively. With the results obtained two groups of cows, divided in high and low parasite burden, were conformed for each method, and milk production was then compared between groups. When cows were separated by the EPG method (EPG=0 (N=106) vs. EPG>0 (N=44)) a difference of nearly 800 l of milk per cow per lactation was found (P<0.05). On the other hand, milk production between groups separated by Pepsinogen (mUtyr ≤ 1000 vs. mUtyr > 1000) or by anti-Ostertagia (ODR ≤ 0.5 vs. ODR > 0.5) results did not differ. Interestingly, proportion of cows in each group differed between methods (P<0.0001), and the anti-Ostertagia method yielded significantly more cows in the high index group compared to results using the EPG or Pepsinogen method. No correlations were found between parasite indexes determined by the different methods. High parasite burden estimation found may be ascribed to the production system, fully grazing all year round, and to the sampling time, at the beginning of lactation with cows in negative energy balance and depressed immunity. The fact that the cows were born and reared outside, on pasture with continuous nematode larvae exposure, may also account for the results obtained. In conclusion, EPG counting during the first postpartum month may be a useful tool for the diagnosis of production impairment induced by high nematode burden in adult grazing dairy cows. The anthelmintic treatment of only the EPG-positive recently calved cows would improve milk production, while reducing selective pressure on nematode population for the development of resistance.

Evaluation of a larval development assay for the detection of anthelmintic resistance in Ostertagia circumcincta.

Two experiments were carried out to evaluate a larval development assay for the detection of anthelmintic resistance in O. circumcincta. In Experiment I, the dose responses to levamisole (LEV), thiabendazole (TBZ) and ivermectin (IVM) of 8 isolates of O. circumcincta were measured 34 days after infection (DAI). Four of these isolates were shown to be resistant to 1 or more anthelmintics. With 2 exceptions, all isolates considered to be resistant had higher LD50 values than the susceptible isolates for that anthelmintic. One exception was isolate RM8, which was considered to be resistant to all 3 anthelmintics based on faecal egg count reduction tests in goats, but the LD50 value for LEV did not differ from that for the susceptible isolates. The other exception was an isolate considered to be susceptible to TBZ which had a relatively high LD50 value. In an unrelated trial that was prompted by this finding, this isolate was confirmed to be benzimidazole-resistant. Isolate RM8 and an isolate susceptible to all 3 anthelmintics (SK2) were used in the second experiment, which was conducted to monitor changes in the LD50 values of LEV, TBZ and IVM over time following a single infection of 35,000 infective larvae in young sheep. Faecal samples were collected weekly from 24 to 115 DAI. With all 3 anthelmintics, the LD50 values increased with time to a peak around 50-60 DAI, and then declined to levels similar to those observed soon after patency. This trend was consistent for both isolates. The highest mean LD50 values for isolates SK2 for IVM and TBZ and RM8 for IVM and RM8, respectively, were 1.7 and 1.8 times, and 2.2 and 2.9 times higher than the initial mean LD50 values. There was a clear distinction in LD50 values between isolates at each sampling day for both IVM and TBZ. However, as a consequence of the changes in LD50 values with time, the peak LD50 values of IVM for isolate SK2 were higher than the minimum LD50 values of isolate RM8. As there was no apparent difference in LEV efficacy between these 2 isolates, the data were pooled. The highest mean LD50 value was 2.3 times higher than the initial LD50 value.

Spiculopteragia spiculoptera, S. asymmetrica and Ostertagia leptospicularis from Cervus elaphus in La Pampa, Argentina.

The nematode species Spiculopteragia spiculoptera, Spiculopteragia asymmetrica and Ostertagia leptospicularis were recovered from the abomasum of wild red deer, Cervus elaphus, in the forest area of the semi-arid Pampeana Region of La Pampa (Argentina) for the first time. Oesophagostomum venulosum and Dictyocaulus spp. were also found.

Effects of tactical late-season treatments with ivermectin on calves naturally exposed to trichostrongyles.

This study was conducted to evaluate the effects of tactical treatments with ivermectin against trichostrongyles in first-season grazing heifer calves in the Danish marshland. A group of Black-Pied Friesian calves was turned out in early May on a permanent pasture naturally infected with trichostrongyle larvae. In late July, when high herbage infectivity started to appear, the pasture was divided into two plots of equal size, which from then and until housing in late October were each grazed by half of the original group of calves. One of these groups was given three anthelmintic treatments with ivermectin at 4-week intervals starting in late July. The other group served as non-treated controls. Ostertagia ostertagi and Cooperia oncophora were the predominant trichostrongyles. Nematodirus helvetianus was observed on few occasions. Although the animals were exposed to a high herbage infectivity from July onwards, the anthelmintic treatments conferred a significant reduction in trichostrongyle loads, as evidenced by an almost complete cessation of egg excretion and a significant lowering of pepsinogen and gastrin levels in the blood. This was reflected in higher weight gains.