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RPCV (2015) 110 (593-594) 60-64

Influence of weather conditions on egg production of Fasciola hepatica in cattle in southern Espírito Santo, Brazil

[Influência das condições climáticas na produção de ovos de Fasciola hepatica em bovinos no sul do Espírito Santo]

Anderson S. Dias1,2, *, Jackson V. de Araújo1, Fábio R. Braga1,André C. Puppin2, Wilber P. Ribeiro2

1Universidade Federal de Viçosa, Viçosa, MG 36570-000, Brazil2Faculdade de Castelo

Summary: The liver fluke Fasciola hepatica is an important helminth that shows worldwide distribution and it is responsible for considerable losses in ruminant livestock. This helminth is zoonotic and possesses indirect life cycle and its dispersion, sur-vival and capacity to infect animals depends of weather conditions in environment. This work aimed to compare the production of F. hepatica eggs recovered in faeces of cattle in different seasonal weather conditions in the south of Espírito Santo State. The exper-imental assay was carried out in a farm, during 12 months. Twelve crossbred cattle were established in area with natural transmission of F. hepatica. Fortnightly, faecal samples were harvested directly from the rectum of the animals and subjected to sedimentation technique to count of eggs. Number eggs were analyzed by anal-ysis of variance (F test) at 5% probability. Correlation test was performed between the same data above cited. No difference of mean number of eggs per gram of faeces of the samples col-lected between periods of rain (October-March) and dry (April-September). The correlation between climate variables and the number of eggs was low. According to the weather conditions reg-istered in experimental assay, it is possible that the animals to be infected by F. hepatica during all the year. Months in which mean temperature and rainfall were more elevated it was corresponded to subsequent by increase in the number of F. hepatica eggs veri-fied through of parasitological examination, this fact signified that these weather variables showed some influence in intensity of in-fections of this animals.

Keywords: Liver fluke, Fasciola hepatica, egg production, cli-matic conditions, parasitological diagnosis, ruminants.

Resumo: A Fasciola hepatica é um importante helminto cos-mopolita e é responsável por perdas consideráveis na produção de ruminantes. Esse helminto é zoonótico e possui ciclo de vida indireto e sua dispersão, sobrevivência e capacidade de infectar animais dependem de condições climáticas presentes no meio. Este trabalho teve como objetivo comparar a produção de ovos de F. hepatica recuperados nas fezes de bovinos em diferentes condições climáticas sazonais no sul do Estado do Espírito Santo. O ensaio experimental foi realizado em uma fazenda, durante 12 meses. Doze bovinos mestiços foram estabelecidos em uma área com transmissão natural da F. hepatica. Quinzenalmente, as amos-tras de fezes foram colhidas diretamente do reto dos animais e submetidos a técnica de sedimentação para contagem de ovos. O

número de ovos foi analisado por análise de variância (teste F), a 5% de probabilidade. Foi realizado o teste de correlação entre os mesmos dados acima citados. Não houve diferença no número de ovos por grama de fezes de amostras coletadas entre os períodos de chuva (outubro a março) e seca (abril-setembro). A correlação entre variáveis climáticas e o número de ovos foi baixa. De acordo com as condições meteorológicas registadas, é possivel que os an-imais sejam infectados por F. hepatica durante todo o ano. Meses no qual a média de temperatura e pluviosidade foi mais elevada corresponderam a subsequente aumento no número de ovos do agente, significando que essas variáveis climáticas apresentam certa influencia na intensidade de infeção dos animais.

Palavras-chave: Fasciola hepatica, número de ovos, condições climáticas, diagnóstico parasitológico, ruminantes.

Introduction

Fascioliasis is a disease caused by the liver fluke, Fasciola hepatica, that parasite mainly cattle and sheep, it possesses a cosmopolitan distribution and it is zoonotic (Cringoli et al., 2002; Lima et al., 2009). This agent is responsible by relevant economic losses in livestock of ruminants principally. The epidemiol-ogy of this disease is closely associated with environ-mental factors, such as temperature, rainfall, relative humidity (Garg et al., 2009; Dutra et al., 2010), and the ecology of freshwater lymnaeids (the intermediate host of F. hepatica) (Acha e Szyfres, 2003). There are sev-eral cross-sectional studies carried out in Brazil based mainly on parasitological diagnostic of eggs in faeces of animals and recovery of helminths from slaughtered cattle. There are many studies about prevalence and incidence of F. hepatica in ruminants, but those that consider parasitic intensity are lacking. Studies con-sidering parasitic intensity are essential to evaluation of economic losses. Studies of analysis of distribution of F. hepatica in a region throught over a longer pe-riod with quantitative diagnostic do not observed also. Efforts to understanding the epidemiological pattern

*Correspondência: andersonsilvadias@yahoo.com.brTel: +(55) 31 37461878; 31 98625058

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and distribution of fascioliasis for a prolonged time con-sidering parasitic charge in the animals needs to be bet-ter studied.

In Brazil, in endemic areas, it is observed that the con-tamination of pastures by metacercariae (larval phase of F. hepatica) can occur almost all the year (Amato et al., 1986). However, in temperate regions, there are a rainy season, when it is raining a lot of and temperature is el-evated and it occurs in the contamination of pasture by freshwater lymnaeids that multiply and carrying meta-cercariae and; a dry season, in which ruminants can be-come infected by metacercariae after grazing in areas previously flooded (Acha e Szyfres, 2003).

Epidemiological dynamics of this agent in temperate regions was evaluated in southern Brazil by Dutra et al. (2010) and Silva et al. (2011). Knowledge of the seasonal distribution of the agent is essential for proph-ylaxis (Cruz-Mendoza et al., 2005). To temperate re-gions there are a lot studies about this agent, however, few studies have been conducted in tropical regions in Brazil to the knowledge of epidemiological dynamics of this agent.

The aim of this work was to compare the production of F. hepatica eggs recovered in faeces of cattle and different seasonal weather conditions in the south of Espírito Santo State.

Materials and Methods

Animals

Twelve crossbred cattle were stabled on a farm locat-ed in the municipality of the Cachoeiro de Itapemirim, Espírito Santo state, Southeastern Brazil (20° 40’ 60.00’’ S, 41° 12’ 0.00’’ W). Animals remained in paddock where had 95,000 m2. This area is characterized by pre-dominance of plains and flooded areas, the elevation is 50 meters. The predominant vegetation is typical Atlantic forest. The climatic classification in the local is Aw, i.e., tropical climate with a dry season according to Koppen-Geiger. The period comprehended to these observations occurred during October 2009 to September 2010.

Animals were maintained under grazing conditions. Cattle were crossbred Holstein x Zebu, and at the be-ginning of the experimental period, animals showed about 10 months and weighted 163.17±10.53 kg. They were previously (3 months before) dewormed orally with a formulation based on abamectin (200 μg/kg body weight) and triclabendazole (10 mg/kg body weight) (Avotan Fasciola, Intervet- Schering Plough®). The experimental assay was approved and certified by Etic Committee in Animal Use/UFV with the process number 052/2011.

Coprological examination

Faecal samples were harvested from the rectum of the cattle (about 20g), fortnightly, during October 2009

and September 2010, and they were subjected to sedi-mentation technique initially described by Dennis, Stone and Swanson (Dennis et al., 1954), modified by Belém et al. (1992). This quantitative technique consists in: to weigh one gram of feces and places it in a Becker and adds 15 ml of double sulfate of po-tassium and aluminium [KAl(SO4)2] solution at 2% and homogenizes it slightly to avoid the formation of bubbles. Then, the content is filtered through a metal sieve (150 meshes/inch) for a sedimentation cup and then added 50ml of detergent solution through the sieve and allowed to sediment for 10 minutes, this proceeding was repeated three times. After this, the precipitate was collected with the aid of a pipette and placed a drop in a lamina, was covered with cover slip and taken under the microscope in a 10x objective and the eggs of Fasciola hepatica are counted.

Weather conditions

The climatic classification in the local is Aw, i.e., tropical climate with a dry season according to Koppen-Geiger. The monthly means of minimum, medium, and maximum temperatures, rainfall and relative humidity were collected at a weather station, near the experimental local. Data were obtained ac-cording to the method recommended by the Penman-Monteith (Allen et al., 1998).

Statistical analysis

Means of number of F. hepatica eggs per gram of faeces of cattle were compared among the rainy (October-March) and dry (April-September) seasons. Mean of number of F. hepatica eggs were statistically analyzed by analysis of variance (F test) at 5% prob-ability. Means of number F. hepatica eggs among two weather stations (rainy and dry) were compared by Tukey test at level 5% probability employing program BioEstat 5.0 program (Ayres et al., 2007). Correlation test between means of number of F. hepatica eggs per grams of faeces and monthly weather variables were conducted. Agreement analyses were performed be-tween monthly mean number of eggs per gram of F. hepatica and monthly climatic variables were con-ducted.

Results

Mean number of Fasciola hepatica eggs per gram of faeces of the experimental period was 1.08, with standard deviation was 0.52 (Fig.1). The largest number of egg per gram of faeces was observed during January 2010 (1.79) and the lower at the beginning, October 2009 (0.20). Means of number F. hepatica eggs per gram of faeces was 26% lower (p>0.05) in drought period (April-September) compared to rainy period (October-March).

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Fig.1 - Mean monthly number of egg per gram of Fasciola hepatica in cattle faeces. Faecal samples were collected from the rectum of 12 cattle, October 2009 to September 2010, forthnightly, and the sample were submitted at quantitative sedimentation techni-que modified of Dennis, Stone and Swanson. The animals were reared at a farm at the municipality of Cachoeiro de Itapemirim, Espírito Santo State, Brazil.

Fig.2 - Mean monthly minimum temperature, medium and maximum rainfall and relative humidity obtained from at a weather station of the region where was carried out the experimental assay, in the municipality of Cachoeiro de Itapemirim, Espírito Santo state, Brazil. The data comprehend the period from October 2009 and September 2010.

The monthly minimum, medium and maximum tem-peratures, relative humidity and rainfall are showed in Fig. 2. The lowest minimum temperature was in Juny 2010 (11°C); the highest, in January and February 2010 (37°C). The monthly mean relative humidity ranged between 67 (June and August 2010) and 80% (December 2009). Rainfall ranged between 12 mm3 (Juny 2010) and 394 mm3 (December 2009).

The correlation coefficient between the number of F. hepatica eggs and the monthly medium temperature was 0.2416 and the ratio between the number of F. he-patica eggs and rainfall was 0.1739 and, was 0.1472, among number of F. hepatica eggs and relative humid-ity. The correlation between climate variables and the number of eggs were very low. These coefficients were not significant (P>0.05).

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Discussion

Animals were dewormed three months before of the experimental assay, which allows us to verify that they were already infected at the beginning of these remarks. The region of this experiment assay had probability of infection of animals during each month and mainly due observations by introduction of tracer’s animals in dif-ferent season in previous assays.

The highest mean of Fasciola hepatica eggs per gram was obtained during January 2010, 1.42, This data is according to Boray et al. (1969), which ob-served that the number of F. hepatica eggs obtained of faeces of cattle are generally low compare to sheep. Experimental assay carried out in the region of study to evaluate the prevalence of cattle with F. hepatica it was verified by Martins et al. (2008) and Alves et al. (2011). They employed parasitological examination and the trematode had prevalence of 21.3, and 14.1%, respectively. However, number of F. hepatica eggs per gram of faeces is not considered in the work of these authors.

Weather conditions such as temperature can influ-ence the development of F. hepatica in intermediates stages, for example, miracidia emerge from the eggs in about 10 days when the average temperature presents around 26°C, which facilitates the occurrence of in-fection of freshwater lymnaeids (Nahm, 1997). During the entire rainy period, temperature was favorable to lymnaeids infection. The contamination of the animal by metacercariae, in local which lymnaeids are es-tablished is permanent (Acha e Szyfres 2003). These areas are those with permanent wet conditions for constant multiplication of lymnaeids, but, often with low and constant number of lymnaeids (Amato et al., 1986). These areas are essential to continuing life cycle of this trematode. In rainy period, another areas sur-rounding can to be flooded and lymnaeids infected can settle in those locals.

In this experimental assay, the paddock was partially flooded and wet during all experimental period, and the presence of lymnaeids was verified on site during dry and rainy seasons. High rates of rainfall were verified during this period and add at low altitudes, these factors favored positively the contamination of the environ-ment and animals by F. hepatica. What was verified also in studies of Dutra et al. (2010) and Silva et al. (2011).

Temperatures above 10°C allow the development of larval stages of F. hepatica in the parenchyma of lym-naeids and that medium temperatures (10-20°C) are ideal for the development of cercariae in lymnaeids (Acha e Szyfres 2003). Throughout the trial period, the temperature showed values from 12 to 37°C (Fig. 2), these temperatures supported the infection of the lym-naeids by miracidia of F. hepatica.

Rate of humidity may be contributed positively to mitigate the drying of the soil, and thus, the multiplica-tion of lymnaeids to be supported and to viability to

hatching of F. hepatica eggs in faeces (Rangel, 1999). In this assay, rate of humidity favored multiplication of them.

Increase of population of lymnaeids depends on the amount of rainfall, on the other hand, high tempera-tures (above 35°C) contributes to reduce drying of the soil and this disfavored increase of population of lym-naeids (Amato et al., 1986). The infection rate of lym-naeids by F. hepatica depends on the rainfall, which favored the multiplication of lymnaeids when it is ele-vated (Rangel, 1999). These events favored increase of the population of lymnaeids and increase of infection these by miracidia of F. hepatica. It is waited that, de-vice at this, after one or two months, it occurs increase of infection of these animals, and in consequence, in-crease of production of F. hepatica eggs in faeces. In this experimental assay, this can to be observed, even if minus intensive.

In Figure 1 and 2, it can be seen that after one to two months, after to increase rainfall (for example, of October to November and of March to April), there is increase production of F. hepatica eggs. And the same extent, it is found that when a reduction occurs in the rainfall, the same occurs in egg production. Egg pro-duction is a reflection of reinfection of animals.

Conclusion

The weather conditions found made possible that the cattle can be infected by F. hepatica in this region both rainy and dry seasons. Although the level of infection of cattle higher in the rainy season, which corresponds to a greater production of eggs during this period.

Acknowledgments

The authors would like to thank FAPEMIG, CNPq, CAPES and CAPES/FINEP for the financial support and grant concession. And too the farmer José Puppin by the animals and Castelo Faculty by technical base.

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