Investigating Brucellosis: Prevalence And Attitudes

Researchers from the Royal Veterinary College in the UK and Kafrelsheikh University in Egypt look at brucellosis in Egypt, its prevalence, risk factors and livestock owners' knowledge, attitudes and practices.
calendar icon 7 June 2011
clock icon 12 minute read

Abstract

Background

Brucellosis is regarded as one of the major zoonotic infections worldwide. It was first reported in Egypt in 1939 and is now endemic, the predominate species of Brucella in cattle and buffalo in Egypt is B. melitensis. The aim of the study was to estimate seroprevalence of Brucella spp. in cattle and buffalo reared in households in an Egyptian village, identify risk factors for animals testing seropositive and to assess the knowledge, attitudes and practices (KAPs) of livestock owners with regards to brucellosis.

Methods

A cross-sectional study was carried out in a village in Menufiya Governorate of Egypt. In June and July 2009, 107 households were selected using systematic sample and all lactating cattle and buffalo present in the household were sampled and tested for antibodies against Brucella spp. In addition, a questionnaire collecting information on potential risk factors for Brucella spp. infection in cattle and buffalo was administered to the household member responsible for rearing the livestock. Between December 2009 and February 2010 households were revisited and a second questionnaire regarding KAPs associated with brucellosis was administered.

Results

True individual and household seroprevalence were estimated to be 11.0 per cent (95 per cent CI: 3.06 per cent to 18.4 per cent) and 15.5 per cent (95 per cent CI: 6.61 per cent to 24.7 per cent), respectively. Cattle and buffalo kept in a household with sheep and goats had 6.32 (95 per cent CI: 1.44 to 27.9) times the odds of testing seropositive for Brucella spp., compared to cattle and buffalo that were not. Most participants in the study stated that livestock owners assist in the parturition of ruminants without wearing gloves and that some farmers sell animals which they suspect are Brucella infected to butchers or at market. Many participants made their livestock’s milk into cheese and other dairy products without pasteurising it.

Conclusions

Brucellosis was endemic at high levels, in the current study. Although livestock owners had good general knowledge of brucellosis, they still appeared to participate in high-risk behaviours, which may contribute to the high seroprevalence in the area. Veterinarians, public health authorities and other community leaders need to collaborate to control the disease in animals and to manage the risk of human exposure.

Discussion

The current study adopted an integrative approach to brucellosis research; investigating the disease from both a veterinary and human health stand point. Individual and household seroprevalence of Brucella spp. in cattle and buffalo was estimated to be 11.0 per cent (95 per cent CI: 3.06 per cent to 18.4 per cent) and 15.5 per cent (95 per cent CI: 6.61 per cent to 24.7 per cent), respectively, confirming that brucellosis was endemic in the studied village. Although, caution should be taken when interpreting point estimates due to their low precision, reflected in the wide confidence intervals. The study also identified a potential role for sheep and goats in the transmission of Brucella spp, to large ruminants and went on to look at how human behavior may influence the spread of the disease, both between animals and from animals to humans.

Unbiased estimates of seroprevalence of brucellosis are lacking in Egypt and therefore comparisons with estimates of Brucella spp. seroprevalence from other studies have to be made with caution. However, they are higher than those obtained in previous studies in different governorates of Egypt by Samaha et al in 2008, who estimated an overall seroprevalence of 5.44 per cent in cattle and 4.11 per cent in buffaloes.

Although animals were tested for antibodies against Brucella spp. as oppose to Brucella spp. organisms, recovery from Brucella infection in ruminants is rare and animals usually remain infected for life therefore it is likely that seropositive animals were still infected. Therefore, the seroprevalence estimates provide information on the proportion of cows and buffalo in the village which are potentially shedding Brucella organisms in milk and during parturition, posing a public health threat. If any cows or buffaloes in the study were vaccinated against Brucella then seroprevalence may have been overestimated but the veterinarian, who had worked in the village for many years, was certain that no animals in the village were vaccinated.

One limitation to the current study is that the organism large ruminants were infected with was not isolated and typed, however, B. melitensis is the predominant Brucella species in Egypt. In addition keeping sheep and goats in the household was the primary risk factor for cattle and buffalo testing serologically positive for Brucella spp., which is consistent with other studies in areas where B. melitensis is the predominant species present, therefore it is assumed that seropositve cattle and buffalo were infected with this species. Species (cattle vs. buffalo) was acting as a negative confounder for the association between Brucella spp. and keeping sheep or goats in the household; buffaloes appear to be less likely to be seropositive than cows, however, households which had buffaloes tended to be larger and hence were more likely to have sheep and goats. The association between species and Brucella spp. was probably not significant due to the low numbers of buffaloes sampled in the study.

Highly homogeneous production management systems were observed in the village, which may explain why no other risk factors for an animal being seropositive for Brucella spp. were identified. Alternatively, perhaps there is little transmission of the disease between cattle and buffalo and maintenance of Brucella spp. in these species is entirely dependent on the small ruminant population in the village. This study focussed on brucellosis in large ruminants and no sheep or goats were tested in the village. Although it would have been useful to test sheep and goats for Brucella spp., a recent study, in 40 villages from nearby Kafrelsheikh governorate estimated that the village flock of small ruminants was infected in more than 60 per cent of villages, village flocks are mobile and used for breeding with household animals. In the same study overall true prevalence of Brucella spp. in sheep and goats, was estimated to be 13.5 per cent (95 per cent CI: 9.3 per cent to 17.7 per cent) and 12.5 per cent (95 per cent CI: 8.6 per cent to 16.4 per cent), respectively. These estimates indicate that Brucella spp. is likely to be present in small ruminants in the village, possibly at a high level.

The high level of awareness of the disease in the village is consistent with an endemic situation. Most participants responsible for rearing livestock were aware of brucellosis and were knowledgeable about the susceptibility of different animal species. There appeared to be a higher awareness of the disease in cattle and buffalo than sheep and goats, which may be because more households kept cattle or buffalo (≈80 per cent) compared to sheep or goats (≈30 per cent). Also, as an abortion in a cow or buffalo is likely to have a greater economic impact on the household than an abortion in sheep or goats, there may be more awareness of disease events in large ruminants. Participants had very accurate knowledge of the main clinical signs of brucellosis in ruminants and the transmission pathways from animals to humans.

Despite the high degree of awareness and accurate knowledge of the disease, its transmission and its effects, most people would not separate animals that aborted from other household animals. This is one of the major risk factors for disease transmission between animals as susceptible animals can be infected via contact with infected animals or contact with aborted materials or products of parturition. This probably demonstrates the lack of facilities for isolation of suspected and/or infected animals in the current smallholder system. Furthermore, in such a hyperendemic setting and given that infection is often subclinical and cattle and buffalo may not always abort, livestock owners may accept that the disease is widespread and that infection is rarely avoided by separating their aborting or calving animals from the rest of their herd.

According to the results farmers may sell animals which abort to the butcher, if ruminants infected with Brucella spp. are often sent for slaughter this may mean abattoir workers may be at a high risk of occupational infection with Brucella spp. The results also indicate that some farmers may sell animals in markets if they believe they are infected with Brucella spp. This may increase the transmission of brucellosis, not only between households in the same village, but also between villages and even larger geographical areas as animals purchased at a market can be moved without restriction to anywhere in Egypt.

When these issues were discussed with participants during the interview most mentioned that it is easier to sell animals on than to notify the veterinary authorities and wait until they test and slaughter the positive animal. This is also more economical as, according to the participants and veterinarians, the compensation received is less than 20 per cent of the market value of the animal and often takes more than a year to receive. A previous study by Pappas et al (2006) investigating patient perceptions of brucellosis in Greece found that around 44 per cent of patients with brucellosis would not allow veterinary investigation as they were worried about the effects on their herd. This indicates that underreporting is likely to be a problem hindering brucellosis control in other areas.

Although farmers are unlikely to report suspected cases to the authorities, they will usually contact the local veterinarian, therefore it seems local veterinarians may not be reporting brucellosis. In the authors experience (MME and YMH), veterinarians will advise households to fatten suspected animals in order to send them to slaughter and will not advise the farmers to get the animal tested, however, they will leave the final decision to the farmer. Veterinarians usually reside in within the village they work in and there appears to be a strong sense of loyalty between them and livestock owners; if they know the farmer, who is often a friend or even a relative, will not get full market value for their animal in compensation there is no incentive for them to report the farmer, especially as they are unlikely to receive any penalty for not reporting. Most local veterinarians are affiliated with the government and there is the opportunity for the government to work more closely with these veterinarians in order to improve the flow of information between themselves and livestock owners. It is likely the only way livestock owners and veterinarians will begin reporting the disease is if adequate compensation or replacement animals are received.

Cattle and buffalo infected with Brucella spp. excrete high concentrations of the organism in their milk, placental membranes and aborted foetuses. Therefore there is a risk of humans becoming infected via direct contact with their animals and through consumption of their dairy products. Most people in the village assist in the parturition and abortion of ruminants (cattle, buffalo, sheep and goats) and handle foetal membranes and aborted foetus without wearing any protective gloves or masks, even though most are aware these are high-risk activities. Placentas and aborted foetuses are disposed by most people into water canals, which can be a source of infection since most animals in this area had access to the water canals for drinking and bathing. B. melitensis has recently been isolated from catfish in water canals in the area indicating that the water is heavily polluted by animal waste. This may also present a new potential route of human infection. In addition, other species may be involved in the transmission of the disease in the village; Brucella melitensis biovar 3 (which is the most common isolate of Brucella spp. in Egypt) has previously been isolated from dogs and rats. Seroprevalence in these species can be higher close to positive herds; in Damitta governorate all three dogs and 14.3 per cent (10 out of 70) rats trapped near a large seropositive dairy herd were also Brucella spp. seropositive. Rats are often found near canals and dogs also use these canals for bathing, therefore these species could aid the spread of Brucella spp.

With regard to the risk of human exposure to Brucella spp. via drinking milk, the results suggest this is negligible since all participants’ boiled raw milk before consumption. However, there seems to be a potential risk of exposure from other dairy products processed and consumed regularly in more than 80 per cent of households, such as cheese homemade from raw milk. In the Egyptian governorate of Damietta, Brucella melitensis biovar 3 has been isolated from soft white cheese and yoghurt on sale in dairy shops, the products were made from cow’s milk which was not heat treated.

Although the results obtained for this village cannot be generalised to other villages in the area, there was no prior information regarding brucellosis that could have directed the study to this village because of a high seroprevalence. Brucellosis is considered endemic throughout Egypt and husbandry practices are similar to those observed in this village, it is therefore possible that the epidemiology of Brucella spp. may be similar in other rural areas.

The difficulty of implementing a comprehensive brucellosis control programme in Egypt has been highlighted in previous reports. These results add to the body of evidence that have identified a critical role of small ruminants in the maintenance and transmission of brucellosis in large ruminants and realistic interventions targeted at small ruminant brucellosis are needed. Until decisive effective action is taken to reduce the incidence of ruminant brucellosis, the local population will have a high risk of exposure.

Public health education could contribute to risk mitigation and should focus on cost-effective strategies to reduce occupational exposure and consumption of unpasteurized dairy products. All participants were interested in the public health education the interviewer provided and some suggested this should be presented as a poster in public places, the interviewer was also asked to ive public talks in order to disseminate information to the whole community. This is a good indication that there is potential for promotion of improved husbandry and dairy processing practices that could reduce the risk of exposure, not only to Brucella spp, but also to other zoonotic pathogens. Recommendations should be achievable and take into account that the livelihoods of most rural residents depend on the few animals they own.

Conclusions

Brucellosis is endemic at high levels among the large ruminant population of the studied village in the Nile Delta region of Egypt, where the main risk factor for cattle and buffalo seropositive status is the presence of sheep or goats in the same household. Animals suspected of having brucellosis are much more likely to be sold to the butcher or in the market than reported to the necessary authorities. Given the observed seroprevalence and reported practices, in the studied population, there is a high risk of occupational exposure of Brucella spp. in livestock keepers, whilst assisting in parturition or abortion of ruminants. There is also the potential for human exposure through consumption of dairy products processed from raw milk that are regularly consumed in most households.

June 2011

Further Reading

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