RESEARCH WORK

 

 

 

Epizootiology of gastrointestinal trichostrongylosis in sheep subject to selective antiparasitic treatments in Cuba

 

 

 

J. Arece1, Y. López1, G. Torres-Hernández2, R. González-Garduño3and J. G. Rodríguez-Diego 4

1 Estación Experimental de Pastos y Forrajes Indio Hatuey, Universidad de Matanzas Camilo Cienfuegos, Ministerio de Educación Superior . Central España Republicana, CP 44280, Matanzas, Cuba
2 Programa de Ganadería, Instituto de Recursos Genéticos y Productividad, Colegio de Postgraduados, México
3Unidad Regional Universitaria Sursureste, Universidad Autónoma Chapingo, México
4 Centro Nacional de Sanidad Agropecuaria (CENSA), Cuba
E-mail: arece@ihatuey.cu

 

 

 


ABSTRACT

The epizootiology of gastrointestinal trichostrongylosis was evaluated for two years in a flock of 72 Pelibuey ewes, with average age of four years, subject to a selective treatment scheme based on a previous epizootiological study and the use of the FAMACHA© chart. The ewes were dewormed at three moments: at lambing, amid the dry season and at weaning; during the rest of the year the strategy of selective treatments through the color of the ocular mucosa was applied. The fecal egg count (FEC), color of the ocular mucosa, hematocrit and body condition were determined through sampling; as well as the effect of season and reproductive status on the parasite rate, by means of a variance analysis. There was predominance of Haemonchus spp., with seasonal trend in the FEC, which was higher during the dry season. From the animals, 59,1 % showed low infestation (less than 300 epg) and only 6,6 % showed high infestation (more than 4 000 epg), which propitiated a rate of 3,55 treatments per ewe per year. The average hematocrit values were over 25 % in both seasons. Additionally, 98,8 % of the animals showed color of the ocular mucosa between A and C of the FAMACHA© color chart, and the empty ewes were the ones with the highest parasite rate. With the proposed strategy it was achieved that the lambs and the lambed ewes were less infested; however, the non-pregnant ewes showed the highest parasite rates.

Key words: Ewe, Haemonchus, parasite.


 

 

INTRODUCTION

At present, the search for solutions for the control of gastrointestinal parasitism in sheep is one of the greatest challenges for the production of this species. The resistance to the most widely used anthelmintics, as a result of their indiscriminate utilization and the low impact of classical methods for parasite control, is increasingly worrisome (Papadopoulos, 2008). Hence, the urgent need to implement alternative strategies for parasite control to be practical at small as well as at large scale.

There are several strategies for parasite control in sheep, which have been evaluated under different conditions and offer opportunities to be used in a context of integrated parasite control. Among them the use of nematophagous fungi (Waghorn et al., 2003), the selection of resistant genotypes (Hielscher et al., 2006; Goldberg et al., 2012), the use of plants with antiparasitic potential (Nguyen et al., 2005) and the application of selective treatments (Kaplan et al., 2004; Molento et al., 2009, 2011), stand out.

In studies previously developed in Matanzas, with Pelibuey sheep and under silvopastoral system conditions, the prevailing presence of Haemonchus spp. was shown, without manifest seasonality (Arece, 2005). The dominance of this genus allowed to make an initial evaluation of the use of the FAMACHA© color chart for the detection of anemic animals, as a result of infestations by Haemonchus (Arece et al., 2007).

Taking these elements into consideration, the objective of the study was to evaluate the epizootiological performance of gastrointestinal trichostrongylosis in sheep exposed to a strategy of parasite control with directed and selective treatments.

 

MATERIALS AND METHODS

Location. The study was conducted in areas of the Pasture and Forage Research Station Indio Hatuey, of the Perico municipality Matanzas province, Cuba, located between 22º 48' 7·North latitude and 81º 2' West longitude, at 19,01 m.a.s.l.

Animals and design.A flock of 72 Pelibuey ewes was used, with an average age of four years (35 ± 2,5 kg of live weight), subject to a parasite control system based on suppressive treatments at parturition, amid the dry season and at weaning, combined with selective anthelmintic treatments, through the use of the FAMACHA© color chart (Vatta et al., 2001; Bath and van Wyk, 2009).

The ewes grazed from 9:00 a.m. to 3:00 p.m. in a silvopastoral system based on an association of improved and naturalized pastures (Panicum maximum, Dichantium-Bothriochloa complex and Andropogon gayanus) and legume trees (Gliricidia sepium, Leucaena leucocephala and Albizia lebbeck). During the dry season residues of bean harvest were offered to the animals as supplementation, and, additionally, at three fixed moments of their reproductive cycle (in the reproduction campaign, in the last third of pregnancy and in the first 30 days postpartum), they received 400 g of fresh citrus pulp. In the shed of the animals there was drinkable water and mineral salts ad libitum.

Measurements. The feces were extracted directly from the rectum of each animal with a monthly frequency, to determine the FEC as indicator of the parasite infestation, through the technique of enrichment by flotation proposed by McMaster (Arece et al., 2002). A feces pool was made in order to elaborate fecal cultures (Roberts and O'Sullivan, 1952) to obtain and identify third-stage larvae of trichostrongylids (Del Valle, 1975).

In addition, blood samples were extracted by puncturing the jugular vein to determine the packed cell volume or hematocrit, through microcentrifugation (Hansen and Perry, 1994).

Additionally, the body condition (BC) was evaluated (Russel et al., 1969) with a scale from 1 to 5 (1: emaciated animal near death, 5: obese animal), as well as the color of the ocular mucosa through the FAMACHA© method color chart, which has five categories A: intensely red mucosae, E: anemic pallid mucosae (Van Wyk and Bath, 2002).

Statistical analysis. The main dispersion stadigraphs were determined to describe the trends of parasite infestation. The effect of season and reproductive status on parasite infestation was determined through variance analysis. Previously, the data of the FEC were transformed (log FEC + 1) to homogenize the variances and obtain a normal data distribution. The differences among means were determined through Duncan's multiple range comparison test (Steel and Torrie, 1992). The information was analyzed with the statistical pack SPSS® version 18.0 for Windows®.

 

RESULTS AND DISCUSSION

Figure 1 shows the monthly dynamics of the parasite infestation in the two years of evaluation of the parasite control strategy. Compared with previous years (Arece, 2005), when only the clinical condition of the animal was used to perform the dewormings, the global infestation rate of the animals was higher when the directed and selective treatments were applied.

During that period of arbitrary dewormings (2003-2005) more than eight antiparasitic treatments were applied per animal per year, and as a result the fecal egg counts were lower; while since the implementation of the control strategy with directed and selective treatments the number of treatments was reduced to 3,55.

Nevertheless, a high resilience level could be observed in the animals, because, in spite of having high parasite rates, in the two years of evaluation there was not a considerable deterioration of the BC of the ewes (fig. 2).

In this sense, it has been found that the body condition of ewes alerts about any metabolic demand (anabolic or catabolic), such as the one animals show during pregnancy, at lambing or even in case of large infestations by Haemonchus spp. (Hoste and Chartier, 1993). In Morocco, Ouzir et al. (2011) reported that there was no clear relation between that condition and the fecal egg count as a sign of parasite infestation, which was probably related to the prevailing and moderate presence of Nematodirus sp.; however, under the conditions of this study more than 95 % of the FEC corresponded to Haemonchus, which is considered the most pathogenic and virulent parasite among the nematodes that affect small ruminants (Anderson, 2000).

On the other hand, Idika et al. (2012) found, in ewes, that the body condition is modified in case of infestation by Haemonchus contortus or Trichostrongylus colubriformis, and is directly related to the immunological response capacity of the animals.

The resilience of these animals was also shown in the color of the ocular mucosa, which is considered a characteristic of resistance to infestations by gastrointestinal parasites (Torres et al., 2006); that is, as long as the animal can maintain adequate hematocrit levels, it will be expressed in the color of the ocular mucosa and, thus, the productive response will be related to this trait. Of all the animals, 98,8 % had color of the ocular mucosa between A and C; while only 1,12 % was detected as D, which is in correspondence with pale mucosae and severe anemia (fig. 3).

This was manifested in the average hematocrit values in the two years, which were over 25 % in both seasons of the year (fig. 4), and this indicates an effective response of the animals to parasite infestation.

The above-described situation is seemingly related to the combination of selective and directed antiparasitic treatments, together with the feeding conditions guaranteed to the flock with the presence of the silvopastoral system and the strategic supplementation at the moments of higher metabolic demand of the animals. Likewise, it is probable that the consumption of tree species such as L. leucocephala and G. sepium regulates the parasite rate, due to the presence of secondary metabolites that have antiparasitic effects (Hoste et al., 2012). An important role in the protection of the diet protein is also ascribed to these metabolites, especially condensed tannins, which form a tannin-protein complex that is not degradable in the rumen (Min et al., 2003); this would allow the development of a better immune response by increasing the flow of bypass protein to the small intestine.

The season had a significant influence on the parasite infestation rate (p < 0,01) in the two years of the study (fig. 5). The ewes became more infested in the dry season, which coincides with the results of previous research conducted in the Matanzas province by Arece (2005).

This situation could be explained by the interaction of several factors highly related to the nutritional status of the flock, which is associated to the decrease of pasture quality and quantity that is recorded in the dry season (Sánchez et al., 2003). The contrary occurs in the rainy season, in which the grazing areas show better yields and offer better nutritional quality feedstuffs, having repercussion on the immunological status of the animals (Nahed et al., 2003). On the other hand, at moments of low feed availability they do a much lower grazing, which could increase the consumption of infesting larvae (Gruner et al., 1984).

This seasonality in infestation responds to the modifications performed on the management system of reproduction in the flock. Thus, the organization of reproduction by campaigns, concentrating lambings mainly in the dry season, indirectly modulates parasite infestation (Uriarte et al., 2003).

In the two years of evaluation global infestation by trichostrongylids was low (FEC below 300 epg) in 59,1 % of the cases; while 26,4 % had values over 1 000 epg. The existing relation between the FEC with predominance of H. contortus and the color of the ocular mucosa has been proven by the hematophagous character of this parasite (Ribeiro et al., 2012), for which the color chart constitutes an appropriate tool for the selective treatment of the animals (Arece et al., 2007). This practice propitiated the application of 3,55 treatments per ewe per year, from which three were strategically performed on all the animals at fixed moments of their reproductive cycle, with the subsequent saving in drugs and the decrease of the selection pressure that causes the appearance of resistance to antiparasitics.

An additional advantage of the FAMACHA© color chart is the selection of the most susceptible animals in the flock, which constitutes a tool for future plans of selection of animals that are resistant or resilient to gastrointestinal parasitism (Burke and Miller, 2008).

When analyzing the influence of the reproductive status on the magnitude of the parasite infestation, the empty ewes were observed to show the highest egg elimination rates (fig. 6).

This trend changed in the herd from the application of the strategy, because in previous years the lambed ewes showed the highest infestation rates (Arece et al., 2007), which is probably related to the direct effect of periparturient rise (Barger, 1993). This indicates that the highest quantity of treatments is concentrated on the most susceptible animals, which in this case are ewes since the last two weeks of pregnancy until the first 45 days postpartum.

The organization of reproduction by campaigns was adopted as bioproductive strategy, but with the intention to concentrate lambings and facilitate deworming of the animals at that moment, and, thus, decrease the epizootiological effects of periparturient rise.

In addition, it could be observed that the structure of the population of trichostrongylids remained invariable, because Haemonchus prevailed throughout the year over 95 % of the FEC, for which the other species present did not occupy its ecological niche.

It is concluded that the combined method of selective and directed treatments in Pelibuey ewes under silvopastoral system conditions does not modify significantly the epizootiology of parasite infestations, for which its continuity as integrated parasite control strategy in this species is justified.

 

ACKNOWLEDGEMENTS

The authors thank the International Foundation for Science and the Cuban Ministry of Agriculture, for the funding supplied to conduct research.

 

 

 

Received: May 25, 2013
Accepted: October 4, 2014