Introduction

The occurrence of the larvae of Taenia saginata (T. saginata) in cattle musculature causes T. saginata cysticercosis or bovine cysticercosis while the adult worms in human small intestines cause taeniasis (Neva and Brown 1994; Carpio 2002). In humans, T. saginata infestation is accompanied with mild symptoms ranging from nausea, abdominal discomfort, epigastric pain, diarrhea, vitamin deficiency, excessive appetite or loss of appetite, weakness and loss of weight to digestive disturbances and intestinal blockage (Neva and Brown 1994). However, in cattle, heavy infestation by T. saginata cysticercosis may cause myocarditis or heart failure (Gracey and Collins 1992). The life cycle and transmission of the parasite occur most commonly in environments characterized by poor sanitation, primitive livestock husbandry practices, and inadequate meat inspection, management and control policies (Mann 1983; Phiri et al. 2003).The life cycle of the parasite, Taenia saginata, involves humans and cattle the final and intermediate hosts respectively (Lees et al. 2002).

T. saginata cysticercosis is found almost all over the world, albeit at very low prevalence in developed countries. Moderate prevalence levels are seen in southern Asia. High prevalence rates occur in Sub-Saharan Africa, especially in Eastern Africa where it causes an important economic loss due to condemnation of meat (Cabaret et al. 2002). In Ethiopia, reported prevalence rates of bovine cysticercosis in cattle ranged from 2.2% to 3.2% (Teka 1997).

Bovine cysticercosis is one of those animal health problems that reduce export earnings of the country (EARO 2000). It is, therefore, important that due attention be given to this disease to improve the quality and quantity of beef so as to satisfy the domestic consumption and to increase the foreign export revenue. The aim of this study was to know the current prevalence of bovine cysticercosis in cattle using the conventional parasitological methods at Addis Ababa Abattoir, Ethiopia.

Materials and methods

Study area

The study was conducted in Addis Ababa Abattoir. At Addis Ababa Abattoir cattle, sheep, goats and swine are slaughtered and animals for slaughter come from different regions of the country. Daily 700 cattle, 250 sheep, and 75 goats are slaughtered. About 50 pigs are slaughtered per week and the sources of pigs are Addis Ababa, Debre Zeit and Zeway farms. On average 153,000 cattle, 39000 sheep, 3200 goats and 750 pigs are slaughtered annually (DoA 2006). The Abattoir provides fresh meat for different Institutions such as hotels, hospitals and butcheries. The Ministry of Agriculture and Rural Development (MoARD) conducts the meat inspection procedure.

Study animals

Postmortem inspection was conducted on 11227 cattle slaughtered at Addis Ababa Abattoir, which originate from neighboring localities and/or regions such as Orromia, Amhara, Souther Nation and Nationalities etc. Of the animals slaughtered 2500 were Holstein-Frisian cattle breeds culled due to various problems from dairy farms where as the remaining 8727 were local zebu cattle breeds. Particular attention was given to factors such as sex, age, and origin of the animals.

Postmortem inspection

Postmortem examinations were carried out in Addis Ababa Abattoir on randomly selected 11227 slaughtered cattle, between September 2004 and August 2005. Carcasses of these animals were thoroughly inspected; incisions and inspection were done following the methods earlier described (MoA 1972; Okafor 1988; Anosike 2001). In the abattoir both exotic and local zebu cattle breeds were slaughtered. The abattoir was visited three days in a week and was such that the butchers were met in the afternoon while bringing their animals to the abattoir for slaughter. This was done to determine the age and sex of each animal slaughtered. The diaphragm, triceps, thigh muscles, masseter muscle, heart muscle, intercostal muscles, lungs, liver, tongue, kidney, intestinal mucosa and spleen of 11227 cattle slaughtered during the study period were examined for bovine cysticercosis. During the routine meat inspection of these organs one or more incisions were made. The cysts observed were categorized into live and calcified cysts. The cysts were carefully dissected from the tissues and the number in each organ recorded for each animal. At the end of the examination, the cysts collected were taken to the laboratory for further diagnosis following the procedures already reported (Petrovic 1976). The cysts were released using bovine bile or pepsin, usually occurred within 30 to 60 min. The cysts were then identified as T. saginata cysticercosis if there were no hooks on the evaginated scolex (Okafor 1988; Opara et al. 2006).

Statistical analysis

The occurrence of bovine cysticercosis was calculated by dividing the number of animals harboring a cyst by the total number of animals examined. Percentages (%) to measure occurrence and chi-square (χ2) to measure association were the statistical tools applied.

Results

All the cattle slaughtered in the Addis Ababa Abattoir were adults. Of the total 11227 animals inspected, 842 animals were positive for bovine cysticercosis. The prevalence of bovine cysticercosis was 7.5%. The prevalence between Holstein-Frisian cattle breeds and local zebu cattle breeds were described (Table 1).

Table 1 The prevalence of T. saginata cysticercosis infection of cattle in Addis Ababa Abattoir
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The sex distribution of T. saginata cysticercosis infection of cattle was described (Table 2). Of the 11227 cattle examined, 92.06% were adult males. Although more males than females were examined, the prevalence of infection did not show any significant difference (P > 0.05).

Table 2 Sex distribution of bovine cysticercosis infection of cattle in Addis Ababa Abattoir
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On the predilection sites of the cysts 36.6%, 35.6%, 34.9% and 33.4%, of the cysts were collected from the masseter muscles, tongue, heart muscles and triceps muscles respectively. Infection was also recorded from the liver (2.7%), inercostal musceles (1.4%), spleen (0.9%) and intestinal mucosa (0.1%). Bovine cysticercosis was not found in the lungs and kidney (Table 3). The distribution and condition of bovine cysticercosis in slaughtered cattle in Addis Ababa Abattoir, Ethiopia was described (Table 4). The cysts of bovine cysticercosis found in the spleen, intercostal muscles and intestinal mucosa were all live while those in the liver 4 were live and 19 were dead. Both live and dead cysts of bovine cysticercosis were found also in other organs inspected.

Table 3 Predilection sites of bovine cysticercosis cysts in slaughtered cattle in Addis Ababa Abattoir
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Table 4 Distribution and condition of the cysts of bovine cysticercosis in 842 infected slaughtered cattle in Addis Ababa Abattoir
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Discussion

During the present study period, we found that 7.5% of cattle presented for slaughter at Addis Ababa Abattoir, Ethiopia harbored bovine cysticercosis. Previous prevalence rates in Addis Ababa Abattoir, based on routine meat inspection, ranged from 2.2 to 3.2% (Teka 1997). We believe that this is due to the inefficiency of the conventional method of inspection. Cysticerci are easily missed, as they may not be present on routine cuts considering that most cases of cysticercosis are light infections. Moreover, observations indicated that except for the dead, degenerate or calcified cysticerci that usually form white and fibrotic lesions a careless meat inspector could most likely miss out quite a number of viable cysticerci, which blend the pinkish-red colour of the meat and be passed on for human consumption. Differences in the skills and motivation of meat inspectors, the speed of the slaughter activity, and the meat inspection facilities, are among the many other contributory factors.

Our observations showed that the masseter muscles, tongue, heart muscles, triceps muscles and thigh muscles among others were the preferred organs (predilection sites) for the cysts of bovine cysticercosis similar to earlier reports in various endemic areas (Okafor 1988; Pawlowski and Schultz 1992; Opara et al. 2006). It appears that several factors, such as activity of the muscles, age, and the geographical area concerned determine largely the predilection sites in slaughtered cattle (Petrovic 1976; Opara et al. 2006). It was observed that some live cysts were isolated from the intercostal muscles, spleen, liver, intestinal mucosa but not from the kidneys and lungs. Sex-related distribution of bovine cysticercosis infection of the slaughtered cattle in this study showed that sex of the animals and infection were independent. Though more males than females were infected, it could be related to the sample size and not sex. Since the animals slaughtered were all adults it was not possible to compare the relationship of prevalence with the ages of the animals. Breed related distribution of bovine cysticercosis indicated higher prevalence (8.5%) in local zebu cattle breeds than Holstein-Frisian cattle (4.1%). This is may be associated with management system where Holstein-Frisian cattle breeds were from dairy farms having less exposure to contaminated pasture with human excreta while the local zebu cattle breeds were from fattening or extensive management system.

In Ethiopia bush defecation, the habit of eating raw beef dishes such as kitfo and kourt and backyard slaughter might have contributed for the high prevalence of bovine cysticercosis in cattle. Therefore, to reduce the transmission of taeniasis/ bovine cysticercosis, public education to avoid consumption of raw meat, and use of latrines and improved standards of human hygiene were recommended.