Prevalence of gastro-intestinal helminths in free-range ducks in Morogoro Municipality, Tanzania

A P Muhairwa, P L Msoffe, S Ramadhani, E L Mollel, M M A Mtambo and A A Kassuku^*

Department of Veterinary Medicine and Public Health, Faculty of Veterinary Medicine, Sokoine University of Agriculture,
P.O. Box 3021, Chuo Kikuu Morogoro, Tanzania
Muhairwa@yahoo.co.uk
^*Department of Veterinary Microbiology and Parasitology, Faculty of Veterinary Medicine, Sokoine University of Agriculture,
P.O. Box 3019, Chuo Kikuu Morogoro, Tanzania

Abstract

A survey was conducted to assess the prevalence of helminths in free-ranging adult ducks in Morogoro Municipality, Tanzania. The gastrointestinal tracts of 192 ducks (96 ducklings and 96 adult ducks) were examined for the presence of gastrointestinal parasites.

Out of the 192 ducks, 100 (52%) were infected with one or several species of helminths. The average number of helminths per duck was 11, ranging from 1 to 55 helminths per duck. A total of 14 different helminths species belonging to five subfamilies were isolated from the intestinal tract and identified. The identified species were: Ascaridia columba (0.5%), Ascaridia dissimilis (0.5%) Ascaridia galli (23.4%), Capillaria anatis (0.5%) , Capillaria annulata (3.1%), Capillaria contorta (7.3%), Heterakis dispar (0.5%), Heterakis gallinarum (14.1%), Heterakis isolanche (2.6%), Raillietina echinobothridia (0.5%), Raillietina tetragona (10.4%), Subulura brumpti (6.3%), Subulura strongyilina (0.5%) and Subulura sucturia (0.5%). The five subfamilies represented one cestode and four nematodes, whereas no trematodes were shown in the study. Prevalence of gastrointestinal worms was statistically significant higher (P<0.05) in ducklings than in the adult ducks, explaining the higher susceptibility of young birds to intestinal infestations.

The work presents the first record of duck helminths in Tanzania. Further studies on the epidemiology and importance of worms in the growth and productivity of ducks under free range management system are indicated.

Key Words: Ducks, free-range, gastrointestinal helminthiasis, prevalence

Introduction

Muscovy ducks (Cairina moschata) represent about 5% of the estimated 30 million poultry in the country (MOA 1994), however their potential as a source of food and income to people has been underexplored. Much emphasis in poultry research and development has been placed on chickens, which resulted in little information on diseases and management constraints of ducks. However, a small population of ducks, their acceptability across different cultures and less susceptibility to devastating diseases promises for expansion as an income generation enterprise for the poor. Ducks are almost exclusively kept as free range in most rural and urban areas of Tanzania. Despite the minimum input, ducks contribute to family food and income, and they retain the reputation of being more resistant to diseases than chickens.

All free-range managed birds are in constant contact with soil (Pandey and Jiang 1992) which serves as an important reservoir and transmission site for external larval stages of helminths and insects. The later eventually become vectors for helminths. These factors explain the presence of wide range of helminths in chickens in traditional sector in Tanzania, which are partly responsible for low productivity of these birds (Permin et al 1997). Helminth infestations are associated with unthriftness, poor growth due to poor feed conversion rate, reduced egg production and fertility and in acute worm infestations lead to death (Soulsby 1982). However, information on the extent and importance of helminthiasis in ducks in Tanzania is lacking.

In free-range chickens parasitic infestations are often neglected (Pandey and Jiang 1992) despite their significant losses in terms of reduced growth rate and mortality. Studies in chickens have demonstrated that worms can be of great economic importance. In Tanzania one study indicated up to 100% prevalence of worms in scavenging village chickens (Permin et al 1997). These worms were reported to have impact in the health and growth of these chickens thus recommendations for control of these parasites is a necessity. In spite of several investigations on helminths in the chickens, very little has been done on investigating the importance of intestinal helminths in the ducks raised under the same management. This study was therefore designed to investigate the prevalence of gastrointestinal helminths in the free ranging scavenging ducks, ultimately suggesting control measures relevant for free range management.
 

Materials and methods

Study area

The ducks population under study comprised flocks of free range ducks in Morogoro Municipality, Tanzania, 200 Km West of Dar-es-salaam. The sampling included randomly selected ducks from 10 suburbs of the municipality namely Chamwino, Konga, Nanenane, Kilakala, Kihonda, Mafiga, Vibandani, Mwanza, Karume and Kiwanja cha Ndege. All ducks in the study area were housed in the backyard and were allowed to scavenge freely during the day at the homestead and the area around. All farmers provided water, table and kitchen remains to their ducks. Occasionally, the ducks were provided with cereals. No preventive treatment was recorded to be done by the investigated farmers.

Sampling and sample size

The study was conducted between January and July 2005. For sampling purposes the ducks were categorized into ducklings between 2 and 5 months and adult ducks of 6 months and above. The required sample size was 96 for each age group based on the formula n=1.96² pq/l² by Thrustfied (1995). Since the prevalence (p) of the infestation was not known, a prevalence of 50% was therefore estimated to be within 5% of the true prevalence 95% of the time. After selection of the farmers, middlemen were used to buy a maximum of 6 ducks (3 adult ducks and 3 ducklings) from each flock owner which were used for the survey.

Examination of ducks

The selected ducks were transported in cages to the Faculty of Veterinary Medicine - SUA, helminthology laboratory. Upon arrival the ducks were killed by cervical dislocation and subjected to post-mortem and parasitological examination.

Post mortem and parasitological examination

Post-mortem examination was performed according to Fowler (1996). After decapitation, the trachea, abdominal and thoracic cavity were opened, followed by systematic autopsy examination which included, the oesophagus to the gizzard, the small intestine (duodenum, jejunum and ileum), the caeca, and the ileocaeca-colic junction to the cloaca. Each section was opened longitudinally and the contents carefully washed through a 100µ test sieve. The mucosa was scraped to collect the helminthes embedded in the mucosal layer. Finally, the contents were examined under a stereo microscope and all helminths were counted before being fixed in 70% ethanol for further identification (Soulsby 1982).

Identification of helminths

Helminths were cleared in lactic acid and examined for morphology under the light microscope at 10x magnification. Identification of helminths was performed according to helminthological keys (Soulsby 1982)

Data management

The prevalence i.e p= d/n, where p is the prevalence d= number of individual having a disease at a particular point in time and n=number of individuals in the population at risk at that point in time, of every species was calculated according to Thrustfield (1995). For calculation of statistical association between the proportions of helminths infestation between adult ducks and ducklings the Chi- square test for differences between two independent proportions was applied (Martin et al 1987). Student t-test was applied to measure the differences between means (Martin et al 1987).
 

Results

Worm Species

In total 192 ducks (96 adult ducks and 96 ducklings) from the Municipality were examined, and 100 (52%) were found to harbour one or more of several species of heminths (Table 1).

A total of 14 different worm species were demonstrated in the small intestine and caecum and none was found in the gizzard and trachea. The overall prevalence of species identified in adult ducks and ducklings is shown in Table 1. In total 12 species of nematodes belonging to subfamilies, Ascaridiae, Capillariae, Heterakiae and Subulura were found whereas 2 species under the family Raillietinae were demonstrated. All 4 subfamilies of nematodes were found in both adult ducks and ducklings, while the subfamily Raillietina was found in ducklings only. No trematodes were found in the study. The adult ducks were shown to harbour only 7 of the 14 species while ducklings harboured 10 species. Ascaridia galli was significantly (P<0.05) more prevalent species of worms (23.4%) followed by Heterakis gallinarum (14.1%) and Raillietina tetragona (10.4%).

Prevalence measures of association

The analysis showed that worms were significantly (P<0.05) more prevalent in ducklings than in the adult ducks. The analysis showed that prevalence of helminths in ducklings was significantly (P<0.05) higher than that of adult ducks. Capillaria contorta, Heterakis gallinarum, and Subulura brumpti were significantly (P<0.05) more prevalent in adult ducks compared with the ducklings.

Worm burden measures of association

Student-t-test showed that for Ascaridia galli mean number of worms per infected bird in adult ducks was significantly higher than (P<0.05) in ducklings. No significant difference (P>0.05) was observed among other helminths subfamilies including Capillariae, Heterakiae, Raillietina and Subulura.

Helminth infestation with only one type of worm (Table 3) were significantly higher (P<0.05) than either simultaneous infection with 2 or 3 worm species. None of the ducks had more than three species of worms in their gastrointestinal tract.

Discussion

The present investigation demonstrated a total of 14 species of helminthes, which marks the first record of duck helminthes in Tanzania. Generally, the study demonstrated four subfamilies of nematodes and one cestode to be common in ducks in Morogoro Municipality in Tanzania. Although majority of ducks carried a single worm species, mixed infections of up to three worms were recorded, and the number of worms per bird ranged from 1-55. Categorization of sampled birds into adult ducks and ducklings enabled the study to show that helminthes infestations were significantly more prevalent in ducklings than in adult birds.

Several studies on the endoparasites of domestic fowl have been conducted in Tanzania (Msanga and Tungaraza 1985; Permin et al 1997; Magwisha et al 2002), however, there is a dearth of reports on the prevalence and significance of endoparasites of domestic ducks. Utpal and Biswas (1997) found 34.3% endoparasitic infection in ducks in West Bengal India and a total of nine different species of helminths were obtained. Their study showed that trematodes comprised more than 26% of helminthes infestation in the area, where as cestodes and nematodes comprised 9% and 5%, respectively. On the contrary, no trematode was demonstrated in the ducks in the present study. The present findings are in line with Permin et al (1997) observations in chickens where despite 100% prevalence of gastrointestinal helminthes no trematodes were demonstrated. These findings suggest that ducks could be more resistant than chickens to helminthes infestation; however, longitudinal studies in chickens and ducks kept together are required to conclude these observations. Similar to chickens seasonal variations in the availability of free water could have limited exposure of ducks to snails which are the intermediate hosts of trematodes. Lack of exposure to snails, which are carriers of trematodes, could partly explain their absence in this study. Contrary to Utpal and Biswas (1997), who investigated commercial flocks with water ponds for ducks these structures do not exist in the free-range duck management.

Ascaridia galli and Heterakis gallinarum which are potentially pathogenic worms were not shown to have clear physical effect on the health status of ducks. Investigation by Permin et al (1997) showed that body condition score of all chicken infected with worms were below normal. Attempts to correlate the body condition with the burden of helminthes were not successful in the present, because data on performance and of ducks in Tanzania is still missing. However, the present study clearly showed that Ascaridia galli and Heterakis gallinarum are the most significant parasitic conditions in ducks in Tanzania and wherever control measures for endoparasites are in place these should be considered. Raillietina tetragona was shown to be an important cestode of ducklings. Although this is generally considered to be a harmless parasite, it will be interesting to study whether the adult birds can simply clear the parasite without treatment. Further investigations of health status, blood parameters and growth rate of ducks will indicate the relative effect of these worms in ducks.

The present study demonstrated for the first time the occurrence of endoparasites of ducks in Tanzania. It shows further that despite the limited attention in research on disease and management, ducks could be potentially resistant to diseases than chickens. More research on disease and management of free range ducks are recommended to promote duck keeping as another source of income and protein to the poor people.
 

Conclusion

• The present study showed that mixed worm infestations are less frequently seen than single worm infections in ducks. Furthermore mixed infections were limited to only a maximum of three species of helminth parasites per bird. These findings indicate that ducks could be less susceptible to mixed infections in comparison with chickens. Whether these have more significant effect on the health and growth rate of these birds remains to be investigated.

• In comparison with chickens the present findings indicate that use of both anticestodal drugs and antinematodal drugs should be practiced when trying to control helminthes in free range ducks.
   

Acknowledgements

The authors are indebted to DANIDA, for funding the study through PHSL project. We thank Mr Kindamba, L. Komba, G.A. and Mwangoka for technical assistance.

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