Introduction

Parasitism is of supreme importance in many agro-ecological zones and still a serious threat to the livestock economy worldwide (Vercruysse and Claerebout 2001). Gastrointestinal (GI) helminth infections are recognized as a major constraint to livestock production throughout the tropics and elsewhere (Githiori et al. 2004). They cause retarded growth (Kochapakdee et al. 1995), lowered productivity (Perry and Randolph 1999), mortality (Sykes 1994), and high economic losses (Iqbal et al. 1993) thus affecting the income of small holder dairy farming communities. For successful formulation and implementation of an efficient and effective strategic helminth control regime, a periodic surveillance providing significant understanding of the prevalence of GI helminthiasis within given environment and associated risk factors that influence their transmission is required.

Prevalence of GI helminths has been reported ranging from 0.72 to 84.1% in domestic animals from various parts of the world (Bundy et al. 1983; Fikru et al. 2006). There are many associated risk factors influencing the prevalence of GI helminths including age, sex, weather condition and husbandry or management practices (Miller et al. 1998; Mirza and Razzak 1998; Raza et al. 2007; Khan et al. 2009). In Pakistan, several studies have been conducted on ruminant helminthosis of various regions reporting a prevalence range from 25.1–92% (Sarwar 1963; Durrani and Hayat 1964; Siddiqi and Ashraf 1980; Durrani et al. 1981; Mohiuddin et al. 1984; Khan 1985; Marwat et al. 1988; Khan et al. 1989, 2009; Iqbal et al. 1993; Qayyum 1996; Raza et al. 2007). However, these surveys were entirely restricted to the vicinity of veterinary institutions. Perhaps surprisingly, there are various geographical regions in Pakistan which are unexplored insofar as documentation of helminths of different animal species is concerned. According to the Population Census Organization (2008), 81.57% of the population of district Toba Tek Singh (T.T. Singh) is rural and depends mainly on agriculture and livestock for their socio-economic activities. Unfortunately, no report so far has been published on the prevalence of ruminant helminthosis from district T.T. Singh justifying the planning of present research project in the district T.T. Singh.

Materials and methods

Study area

District T.T. Singh (30° 33′ to 31° 02′ north latitudes and 72° 08′ to 72° 48′ east longitudes) is comprised of three tehsils (administrative divisions) viz: Kamalia, Gojra, and T.T. Singh. The study area is mainly cultivated land with some grassland that is used as grazing territory. The climate of the study district is temperate (av. max. temp. = 35°C; av. max. humidity = 67%; av. annual rainfall = 340 mm; Population census organization 2008). June and July are the hottest months (av. max. and min. temp. of 40°C and 28°C, respectively) whereas December and January are the coldest months (av. max. and min. temp. of 17°C and 6°C, respectively). For convenience, the whole year was divided into four seasons on the basis of temperature: (a) summer (May to July; 37–41°C); (b) autumn/rainy (August to October; 29-34°C); (c) winter (November to January; 06-17°C); (d) spring (February to April; 22-34°C).

The questionnaire

A well-structured questionnaire was prepared using closed-ended questions (dichotomous and multiple choice) which was refined through informal and formal surveys (Thrusfield 2007). Included in the questionnaire were: (a) farm and owner details; (b) details of animals including age and sex; (c) type of feeding, i.e., grazing or stall feeding; (d) source of drinking water (ponds, rivers/canals or fresh tap water); (e) farm management and husbandry practices.

Sampling of units

Based on multiple stage cluster random sampling, the number of primary units (Union Councils), secondary units (farms) and elementary units (animals) were sampled using formulae given by Thrusfield (2007). Union councils to be sampled were selected by using a map grid method. A total of 30 union councils, 70 farms, 1,140 cattle and buffaloes each, 660 goats and 840 sheep were entered into this survey. Cattle and buffaloes <2 years of age were classified as young and >2 years as adult, while for sheep and goats young were <6 months and adults were >6 months.

Surveillance

The current longitudinal study was conducted from January, 2008 to December, 2008. A periodic, every 14 days, screening of the selected animals was conducted in order to (a) collect fecal samples to be screened through parasitological procedures and (b) collect relevant information on the pre-designed questionnaire which was used for the determination of risk factors associated with the prevalence of helminthiasis in these domestic ruminants. Climatic data of district T.T. Singh were obtained from the Meteorological Department of Pakistan for the year 2008.

Coprological examination

The fecal samples collected directly from the rectum of selected animals were brought to the Laboratory of Epidemiology, Department of Parasitology, University of Agriculture, Faisalabad. The samples were examined for the quantitative assessment of worm burden using modified floatation technique (Iqbal et al. 2006). The eggs of different parasite species were identified using keys given by Soulsby (1982). The positive samples were subjected to coproculture according to the method described by Zajac and Conboy (2006). The third-stage larvae (L3) were isolated through Baermann test and identified by the descriptions given by MAFF (1986) and Zajac and Conboy (2006).

Statistical analyses

The descriptive data thus obtained were analyzed through multiple logistic regressions and odds ratio (OR) in order to measure the significance of possible associated determinants (age, sex and management conditions) on prevalence of GI helminths (Thrusfield 2007). OR was determined by considering females, young, grazing, ponds and rivers/canals as group 1, while males, adults, stall feeding and tap water were considered as group 2. All the analyses were carried out using SAS (1998) software package at 95% level of confidence.

Results

Prevalence by host

The prevalence of helminthosis was found to be significantly higher (P < 0.05; OR = 1.27) in small ruminants (42.40%; 636/1,500) compared with large ruminants (36.75%; 838/2,280). In small ruminants, the prevalence of GI helminths was significantly higher (P < 0.05; OR = 1.18) in sheep (44.17%; 371/840) followed by goats (40.15%; 265/660). In large ruminants, buffaloes (39.82%; 454/1,140) had significantly higher (P < 0.05; OR = 1.30) prevalence of helminthosis as compared to that of cattle (33.68%; 384/1,140).

Prevalence by parasite

The helminths found in the ruminant population of the study area were Fasciola gigantica, Fasciola hepatica, Haemonchus contortus, Toxocara vitulorum, Oesophagostomum spp., Trichuris spp., Trichostrongylus spp., Ostertagia spp., Cooperia spp., Strongyloides spp., and Moniezia spp. Tables 1 and 2 show the descending order of their abundance in various ruminant species.

Table 1 Sex-wise and age-wise prevalence of GIT helminthes in cattle and buffaloes of district Toba Tek Singh
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Table 2 Sex-wise and age-wise prevalence of GIT helminthes in sheep and goat of district Toba Tek Singh
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Determinants influencing prevalence of GI helminths

Season

Monthly prevalence of all the helminths was significantly higher (P < 0.05) in October (temp. = 33°C; humidity = 54.7; rainfall = 3.8 mm) compared with little or no infection during June (temp. = 37.1°C; humidity = 27.9; rainfall = 27.9 mm) and other months had intermediate values. Thus, seasonal prevalence was highest (P < 0.05) during autumn (48.15%; 455/945) followed in order by spring (44.55%; 421/945), winter (42.54%; 402/945), and summer (20.74%; 196/945). There was an increasing trend in the eggs per gram (EPG; from 500 to 900) at the beginning of the rainy season. A graphical representation of monthly prevalence of different species of GI helminths is shown in Figs. 1 and 2.

Fig. 1
figure 1

Monthly prevalence of gastrointestinal tract helminths in small ruminants of district Toba Tek Singh, Punjab, Pakistan

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Fig. 2
figure 2

Monthly prevalence of gastrointestinal tract helminths in large ruminants of the district Toba Tek Singh, Punjab, Pakistan

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Age of animals

Younger animals were found to be more susceptible (OR > 1; P < 0.05) to helminthosis as compared to adults of the entire host species studied. However, these differences were not found to be significant (P > 0.05) in the prevalence of F. hepatica and F. gigantica (Tables 1 and 2). Mean EPG values were often greater than 900 in the younger animals as compared to those observed in adults (300–600).

Sex

EPG values were not significantly correlated with host sex. However, females of cattle, buffaloes, sheep, and goats were found infected more frequently (P < 0.05) with GI helminths as compared to males. However, there were no sex-related differences in the prevalence of F. hepatica in cattle (P > 0.05) or buffaloes (P > 0.05; Tables 1 and 2).

Area

Among three tehsils, no significant difference (P > 0.05) was found in distribution of GI helminths in the selected animals.

Farm management and husbandry practices

Of the total of 75 selected small holder dairy farms, 57.33% of buffalo farms (43/75), 62.66% of cattle farms (47/75), 90.91% of sheep farms (30/33), 34.62% of goat farms (9/26) had grazing practice. The prevalence of GI helminths was higher (P < 0.05) in the grazing animals compared with those on stall feeding system (Table 3). Also, levels of infection were found to be significantly higher in the animals (P < 0.05) supplied with stagnant ponds as water source for drinking and bathing followed in order by rivers/canals and tap water (Table 3). The OR values of grazing, stagnant ponds and river/canals (OR > 1) indicate a strong positive association with prevalence of GI helminths (Table 3).

Table 3 Impact of on-farm management and husbandry practices on the prevalence (%) of GIT helminthiasis in buffaloes, cattle, sheep and goats of district T.T. Singh
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Discussion

The investigation of different aspects of helminth infection showed that climate was an important factor in determining levels of infection. GI helminthiasis was found prevalent throughout the year but with variable levels of infection in the different host categories and climatic environment. The probable reasons of increased infection of GI helminths in the rainy season may be due to the provision of favorable environmental factors for the development and growth of most helminth species. These factors include: (a) suitable humidity and moisture, provided by warm and wet conditions, that made it possible for the eggs to hatch and increase the development of eggs to L3 (Andrews 1999); (b) a temperature range of 19–32°C, that was favorable for the development and maturation of the larvae of most helminth species (Lima et al. 1990); (c) ample provision of water that facilitated the migration of larvae from manure to the herbage (Lima 1998). In contrast, most of the helminth species are susceptible to desiccation in dry climatic conditions that results from the high temperature at which even eggs fail to develop into L3 (Banks et al. 1990; Tembely 1998; Waruiru et al. 1998). This may be the reason for little or no infection during the warmer months like June and July. The present results are in agreement with previous studies of the same province indicating positive association of climatic factors with prevalence of GI helminths of various host species (Khan et al. 2009).

The helminths recorded in different animals in this study (F. gigantica, F. hepatica, H. contortus, T. vitulorum, Oesophagostomum spp., Trichuris spp., Trichostrongylus spp., Ostertagia spp., Cooperia spp., Strongyloides spp., and Moniezia spp.) have also been reported previously in other localities of Pakistan (Sarwar 1963; Durrani and Hayat 1964; Shah et al. 1980; Siddiqi and Ashraf 1980; Durrani et al. 1981; Mohiuddin et al. 1984; Khan 1985, Marwat et al. 1988; Khan et al. 1989, 2009; Iqbal et al. 1993; Qayyum 1996; Sajid et al. 1999; Raza et al. 2007). In these previous reports, the most frequently occurring GI helminth species were T. vitulorum and H. contortus in large and small ruminants, respectively. However, in the present study of district T.T. Singh, F. gigantica was the most prevalent species of small and large ruminants. This difference may be attributed to regional variations due to climate and farming practices of various regions of the country, especially the use of ponds, the primary habitat of the intermediate host of F. gigantica (Spithill et al. 1999), in the district T.T. Singh as a water source for the grazing animals.

The time available for the development of infective nematode larvae on pasture is relatively longer (Ndamukong and Ngone 1996; Ng’ang’a et al. 2004); than that found in stalls, and this may account for the higher prevalence of GI helminthes in grazing animals. The high parasite prevalence in buffaloes to GI parasites in the present study may be due to their swampy habitat (Banerjee 1991) as this favors the development of many helminth species as well as snail vectors for F. gigantica (Lima 1998; Tembely 1998; Waruiru et al. 1998; Spithill et al. 1999). This is further supported by the highest rate of infection in animals using ponds as a water source followed in order by those using rivers and piped sources. The factors contributing to higher prevalence of GI helminthiasis in sheep may be (a) extensive grazing (Ndamukong and Ngone 1996; Ng’ang’a et al. 2004) (b) habit of grazing close to the ground as compared to goats (Taylor 1985). In contrast, goats (a) are kept on semi-intensive grazing system (Ndamukong and Ngone 1996; Ng’ang’a et al. 2004) and (b) prefer to browse shrubs (Taylor 1985). Our results are not different from those of many other researchers (Onyali et al. 1990; Waruiru et al. 1998; Nginyi et al. 2001; Magona and Musisi 2002; Ng’ang’a et al. 2004; Keyyu et al. 2006; Raza et al. 2007) who have found a direct influence of grazing characteristics on the prevalence of most of GI helminths.

Females were less exposed to pasture contamination due to a higher trend of stall feeding; therefore it was surprising that females of large and small ruminants were affected more frequently with GI helminths than males. Generally, it is assumed that sex is a determinant influencing prevalence of parasitism (Pal and Qayyum 1992; Iqbal et al. 1993; Maqsood et al. 1996; Komoin et al. 1999; Valcárcel and García Romero 1999) and females are more prone to parasitism during pregnancy and peri-parturient period due to stress and decreased immune status (Urquhart et al. 1987). However, some scientists recorded higher prevalence in male ruminants than females as most of the males were kept under grazing practice and females were not grazed during pregnancy (Gulland and Fox 1992; Raza et al. 2007).

Lower prevalence in adults may be due to higher immunogenicity of GI helminths helpful in the generation of acquired immunity in older animals. The hypothesis that older animals can acquire immunity against GI parasites has been supported experimentally by different scientists (Gamble and Zajac 1992; Rajapakse et al. 1994; Colditz et al. 1996; Knox 2000). Similarly, a number of scientists have demonstrated an increased prevalence in young age (Gupta et al. 1976; Starke et al. 1983, Roberts 1990; Raza et al. 2007). However, in our study, prevalence of F. gigantica and F. hepatica were not found to be associated with the age of host (Khan et al. 2009). It is often assumed that due to shorter life span of Fasciola sp., a short-term acquired immunity is developed in the host making them more prone to re-infection (Roberts et al. 1996; Clery et al. 1996). Some scientists reported significantly higher prevalence of Fasciola in older animals as compared to young animals (Shrestha et al. 1992; Ghirmire and Karki 1996; Maqbool et al. 2002; Pfukenyi et al. 2005). Therefore, no explanation can be made for the age differences in the prevalence of GI helminths except for the development of short-term acquired immunity protecting older animals.