Livestock Research for Rural Development 21 (11) 2009 Guide for preparation of papers LRRD News

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An evaluation of the economic losses resulting from condemnation of cattle livers and loss of carcass weight due to Fasciolosis: a case study from Hai town abattoir, Kilimanjaro region, Tanzania

E S Swai and E Ulicky*

Veterinary Investigation Centre, PO Box 1068, Arusha, Tanzania
ESSwai@gmail.com
* District Livestock Office, PO Box 10 Hai, Tanzania
edwuliky@yahoo.com

Abstract

A survey was carried out in Hai town abattoir during the period of August 2004 to August 2005 (13 months) in order to estimate prevalence and economic importance of bovine fascioliasis in slaughtered cattle. Prevalence of fascioliasis was calculated as the number found infected with Fasciola, expressed as the percentage of the total number of cattle slaughtered. A total of 2114 cattle originating from Weruweru –secondary market and local livestock traders were examined.

 

Three hundred and forty one livers (16.1%) of these cattle were condemned for various reasons. Two hundred ninety seven (14.05%) were infected with Fasciola. The monthly incidence was highest during the period immediately before and after onset of the short rain (Vuli). The total economic loss incurred as a result of condemnation of infected livers due to all causes and fascioliasis was approximately 2,096 US$ and 1,780 US$ respectively (1 US $ equiv. to Tsh 1,116/=). Losses due to weight loss were estimated to be 5,943 US$. Finding of this study suggest that fascioliasis is prevalent in cattle, that it causes great economic losses as a result of condemnation of livers and carcass weight loss. Local climatic factors, cattle trade, local management practices by various ethnic groups, presence of snail intermediate hosts are probably the main factors influencing the incidence of disease in the present area of study.  

 

It’s concluded that parasites (including Fasciola spp) contribute significantly to meat loss in cattle raised in Tanzania and therefore more efforts are needed to minimize such loss and save valuable protein rich food needed by the growing population of Tanzania.

Key words: economic impact, fascioliasis, prevalence, slaughtered cattle, Tanzania


Introduction

Parasitism is one of the major bottlenecks to livestock development in the tropics and in Tanzania in particular (Hansen and Perry, 1994; Kassai 1999; Keyyu et al 2003; Max et al 2006). Among many parasitic problems of farm animals, fascioliasis is a major disease, which imposes direct and indirect economic impact on livestock production, particularly of sheep and cattle (Kassuku et al 1986; Hammond and Sewell 1990; Wamae and Ihiga 1991; Menkir et al 2007). Bovine fascioliasis is an economically important trematode infection of cattle in Tanzania (Makundi et al 1998; Keyyu et al 2005). The causative agent for the condition/ disease in this country is Fasciola gigantica and Fasciola hepatica (Walker et al 2008). The life cycle of these trematodes involves snail as an intermediate host (Max et al 2006; Walker et al 2008). Several studies to explain whether the two species exist in Tanzania have shed light on the possible occurrence and distribution of these species (Makundi 2001; Walker et al 2008).

 

Preliminary data on economic loss due to fascioliasis in cattle indicates a reduction in production efficiency by 5% and over 10% in mild and severe infection, respectively (Wamae et al 1998; Mungube et al 2006). Acute losses associated with fascioliasis have also been recorded in East Africa (Maingi and Mathenge 1995). Acute fascioliasis causes a substantial economic loss, which include death, loss of carcass weight, reduction in milk yield, condemnation of affected livers, decline in production (reproductive) performance, predisposition to other diseases and cost of treatment (Wamae and Ihiga 1991; Maingi and Mathenge 1995). Several researchers using slaughterhouse surveys have studied the infection rates of Fascioliasis in domestic animals (Mungube et al 2006; Msanga 1985; Menkir et al 2007). Slaughter house surveys carried out from 1965 - 1984 covering  different eco-climate regions of Tanzania (Lake zone, Mwanza; Northern zone, Arusha; Southern highland zone, Iringa and Mbeya; Usambara Mountains, Lushoto) revealed disease to be prevalent and variable, ranging from 6.5 -71% in cattle, 8-26% in sheep and 12-23% in goats( Hyera 1984; Swai 1985, unpublished)

 

Despite of the several surveys and reports, no (or little) efforts have been made to estimate either the total losses resulting from fascioliasis infection or even partial losses from the condemnation of organs. Therefore, this study was conducted with 2 objectives that are to determine the prevalence of fascioliasis in cattle slaughtered at Hai town abattoir and to estimate the economic loss incurred due to the disease.

 

Material and methods 

Study site

 

The study was carried out between August 2004 and August 2005 in Hai town abbatoir, Hai District of Kilimanjaro region. Hai town (latitude 3 ‘100S and longitude 37’100 E ) is located 30 km west of Moshi municipal and lies within 780 to 850 m above sea level. Hai town has a semi arid climate which, is characterized by a long dry season lasting between June and mid October. Long rains starts in February to June and short rains starts in October to December. The average annual rainfall is about 900 mm and mean monthly temperature ranges between 18oC and 33oC.

 

Study animals

 

The study animals comprised 2114 heads of indigenous Tanzanian short horn zebu (TSHZ) slaughtered at Hai town abattoir. Most were trade animals, brought to the abattoir from distant areas covering long distances. Almost all cattle slaughtered in the abattoir came from Weruweru secondary cattle market, which is approximately 10 km from Hai town abattoir. Weruweru market receives animals from Shinyanga, Hanang, Singida, Mbulu, Kiteto and Simanjiro (approximately 120 km from Hai town). A small proportion of cattle, originate from Rundugai, Naibilie and Kingori – the primary livestock markets near Hai town abattoir.

 

Data collection, pre and post slaughter examination

 

The abattoir was visited daily every month for 13 months. Records of numbers slaughtered, source of slaughtered stock and the liver lesion(s) observed and condemned were noted by meat inspector. All animals presented for slaughter were physically observed a day before or shortly prior to slaughter. Inspection of the animals was made while at rest or in motion for any obvious sign of disease. Post slaughter examination involved visual examination of carcasses and organs (results not shown) with keen attention being directed to livers. Through palpation and incision of dilated or thickened bile ducts, gross pathological lesion of each diseased liver was established and recorded as described by Gracey (1985).

 

Assessment of weight of condemned livers or carcass from slaughtered cattle

 

The average price per kilogram of bovine liver (Av Pl) and beef (Av Pb) for each particular month was obtained through interviews made with local butcher men in Hai town.

 

1) To determine the average weight of bovine liver, slaughter slabs in and around Hai town were visited and 50 bovine livers from animals of different ages were weighed and the average weight calculated. The average (mean) weight of bovine liver was found to be 3.5 kg (Standard Deviation [SD], 0.56, range, 2.5 to 4.5).

 

Prevalence rate (Pf) of the disease was calculated as proportion of liver found/condemned due to fascioliasis over the total number of animal slaughtered.

 

2) The direct loss (DL) resulting from condemnation of bovine liver was calculated using the following formula:

 

DL = TNA x Pf x Av Pl

(TNA) = Total number of animals slaughtered,

 

The average price of liver and beef obtained from businessmen dealing with cattle meat at Hai town during this survey was US $ 1.79 and 1.52 per kg, respectively. The monthly condemnation was used to estimate number of livers condemned due to all causes and fascioliasis. 

 

Assessment of economic implication of condemned livers and carcass weight loss

 

An estimated 10% carcass weight loss due to fasciolasis was adopted basing on Hope Cawdery et al (1997) estimates. The adopted carcass weight loss in (kg) was estimated from fresh, normal and health looking, randomly selected from 20 dressed carcasses already passed for human consumption. These were weighed and the average weights of carcasses taken as the estimate weight of a particular carcass. Average carcass weight (AvCW) in kilograms of Tanzania short horn zebu (TSHZ), 137.5(SD, 14.01, range 110.5 to168.5) was considered to compute the carcass weight loss due to the disease. Thus, carcass weight (CW) loss was derived from the following formula:

 

CW = TNA x Pf x AvCW x 10% x AvPb

 

Statistical analysis

 

Collected post mortem/meat inspection records were entered, edited, validated and performed by Epi-Info (Version 6.04b, Centre for disease control, Atlanta, USA). The test statistics used were mean (x), percentages (%) and chi-square test of independence to compare prevalence with respect to the pathogen effect on livers and to compare monthly prevalence rates of fascioliasis. The reference level for each monthly proportion value was that with the largest sample size. Because of aggregate data (other causes of liver condemnation), economic loss (impact) analysis reported in this study was only made for fascioliasis.

 

Results 

Slaughter characteristics and prevalence estimates

 

In between August 2004 to August 2005, a total of 2114 bovine heads were received in Hai town abattoir for slaughter. High number of slaughters was recorded in December 2004.  Monthly mean ( SD) slaughter was estimated to be 162 18.8(range, 134, 207). Three hundreds and forty one livers (16%, 95%Confidence interval [CI], 14.6, 17.7) were diagnosed and condemned as unfit for human consumption because of various reasons. Of the condemned livers, fascioliasis accounted for a higher rate (87%), closely followed by calcified cyst (7.3%), cirrhosis (3.2%), Hydatid cyst (0.87%) and abscess (0.87%). Overall liver condemnation due to fascioliasis during the entire study period was estimated at 14.04 % (95%CI, 12.5-15.6).  Monthly prevalence rate results and pattern of liver condemnation due to all causes and fascioliasis are shown in Figure 1.



Figure 1.  Monthly prevalence (%) of condemned livers due to all causes and Fascioliasis in Hai town abattoir
between August 2004 to August 2005.(error bar represent 95% confidence interval of proportion)


There was significantly high proportion of liver condemnations during the period of August to November 2004 compared to other months of the year (p< 0.05).

 

Economic significance of fascioliasis

 

Extrapolated livers and carcass weight losses (in kgs) and monetary value due to fascioliasis are given in Table 1 and Figure 2.


Table 1.  Losses due to liver condemnation and carcass weight loss – Aug 2004-Aug 2005

Month

Number of
animal killed

Total number of liver condemned-all cause (Fascioliasis)

Liver loss

(all causes), kg

Liver loss

(due to Fascioliasis), kg

Carcass weight
 loss, kg

Aug ‘04

170

44(40)

149

137

538

Sept’04

156

33(30)

115

104

408

Oct’04

148

31(29)

104

98.4

387

Nov’04

138

29(25)

101

86.9

342

Dec’04

207

15(14)

50.7

43.5

171

Jan’05

134

17(16)

56.3

51.6

203

Feb’05

154

22(15)

75.5

48.5

191

March’05

172

26(24)

90.3

78.3

307

Apr ‘05

151

20(17)

68.7

58.1

228

May’05

162

26(24)

90.7

79.4

312

June’05

167

22(18)

75.9

58.5

230

July’05

175

25(20)

85.7

67.4

265

Aug’05

180

31(25)

107

81.9

322

Total loss, kg

341(297)

1,169

993

3,902




Figure 2. Monthly monetary loss due to carcass and condemned livers (all causes
and Fascioliasis)  in Hai town abattoir during August 2004 to August 2005


Overall, condemned edible liver due to all causes and fascioliasis was 1,169 and 993 kgs, respectively. Corresponding carcass weight loss was 3,902 kgs. The respective monetary loss due to liver condemnation as a result of all causes and fascioliasis was US$ 2,096 and US$ 1,780 respectively, whereas carcass weight loss was valued at US$ 5,943

 

Discussion 

Analysis of the meat inspection records from Hai town abattoir presented here showed that fascioliasis was relatively common in cattle. Results from this study also show that Hai town abattoir slaughters on average 162 cattle per month, which implies a total of 6 kill per day. Out of a total of 2114 indigenous heads of cattle slaughtered and examined, 297(14.04%) were found affected with fascioliasis. The obtained prevalence was higher than the value reported from Nigeria and Kenya of 8% and 8.2%, but lower than the reported figure of 37% and 46% from Zimbabwe and Zambia basing on the traditional slaughter stock (Okoli et al 2000; Kithuka et al 2002; Pfukenyi and Mukaratirwa 2004; Phiri 2006). The overall prevalence of fascioliasis (14.04%) obtained in this study appear to be lower than that obtained in Southern Highland zone of Tanzania (Hyera 1984), however, comparable to 12% obtained in Lake zone and Arusha Municipal abattoir (Swai 1985 unpublished; Msanga 1985).

 

A seasonal pattern of infection could be established from the present results. The prevalence was fairly constant from January 2005 to July 2005, but an increasing trend was recorded during the period of August (in both years) to November suggesting for higher infection rates of Fasciola spp in these months. The monthly variation in the prevalence of fascioliasis may be associated with climate changes, which affect field conditions and influence the frequency of cattle/water contact. Epidemiological studies carried elsewhere in Tanzania showed seasonality differences with respect to helminth infections, with high prevalences of fascioliasis being detected towards the end of the dry season and early part of the rainy season; an observation which is comparable to the finding of the current study (Keyyu et al 2005). Liver fluke transmission is dependent on the presence of its snail intermediate host; therefore distribution of the parasite is limited to geographic areas where the appropriate snail species is present. The seasonality pattern of prevalence detected in this study is also in agreement with other investigators, who suggested that, heavy mortality as a result of fascioliasis occurred during the dry season (Ogunrinade 1981; Hyera 1984; Makundi 2001). This monthly prevalence may also be explained in terms of source of animals, keenness of meat inspector, status of meat inspection facilities (i.e. adequate lights), seasonal migration in search of water and fodder during the dry season (Githiga et al 1995). The later observation might have also contributed to the low prevalence rates recorded in this study. Because of the reduction in water level at this time, cattle are able to graze in the affected areas and thus acquire an infection. On the other hand, cattle harboring high infection may survive long enough into the rainy season. Some studies have shown that once ingested by ruminant host it takes apparoximately10 to 12 weeks for the infection to be patent (Kaplan 2001). This development process of parasite within host body may in part explain the variation of infection severity between months. Therefore, a higher incidence of fascioliasis would be recorded at the end of the dry season or beginning of the rains. Source of the slaughter animals, especially from primary source of origin to the secondary market (Weruweru) in this survey could not accurately be ascertained due to the general inadequacy of information from the few presented cattle movement permits. Scanty retrieved information revealed that, some of the slaughtered cattle came from Mbulu and lowlands parts (swampy) of Hai town. The potential of these areas as a source for Fasciola infection require further investigation.

 

Pathological lesion of the affected livers causes considerable loss to affected organs or carcasses due to condemnation of affected parts. Live animal affected by liver fluke end up loosing weight and this substantially reducing the value of carcasses meat. Considering the amount of liver and carcass weight loss detected in this survey, which is valued at approx US$ 9,818 equiv to about US $ 4.6 per each slaughtered animal; this loss is substantially high. In Kenya, Wamae et al (1998) reported an average loss of 12 to 23 US$ in yearling Friesian and Boran cattle experimentally infected with Fasciola gigantica metacercariae. Liver condemned in Hai town abattoir represent a considerable loss of valuable protein and revenue. No attempts were made to retrieve some of the livers condemned so that they could be processed to commercial meat meal to be used as pet food or other wise. This indicated that the estimated loss due to the disease in the abattoir was quite considerable.

 

It is worth noting that realistic economic losses assessment due to Fasciola infection is difficulty and our estimate data and procedure used in this study should be interpreted with caution. To be able to accurately evaluate economic losses, vital parameters such as mortality rates due to disease, chronic ill effects (weight gain, feed conversion efficiency, intercurrent disease, poor carcass conformation, malnutrition, decreased fertility and milk yield), anthelmintic treatment costs should be available and consulted(Ogunrinade and Ogunrinade 1980; Kaplan 2001). These vital parameters were not employed in this study due to various reasons including inadequacy of general livestock production and disease data. Therefore our estimates are likely to be at variance with the true losses in cattle. However, consistent with the results of studies by Berhe et al (2009), the findings of the study indicates losses due to Fasciola infection is substantial and suggests that there is a need for a better structured survey to elucidate the magnitude of the actual losses and emphasise the need for adequate control measures.

 

Conclusions and recommendation 


Acknowledgements

The authors wish to acknowledge the cooperation of meat inspector, livestock traders and butcher men and Hai district field staff for their considerable support and help. This paper is published with the permission from the Director of veterinary services in Tanzania. This study was funded by PACE –disease surveillance fund.

 

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Received 29 September 2009; Accepted 11 October 2009; Published 1 November 2009

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