Genomic epidemiology of Escherichia coli: antimicrobial resistance through a One Health lens in sympatric humans, livestock and peri-domestic wildlife in Nairobi, Kenya

BACKGROUND

Livestock systems have been proposed as a reservoir for antimicrobial-resistant (AMR) bacteria and AMR genetic determinants that may infect or colonise humans, yet quantitative evidence regarding their epidemiological role remains lacking. Here, we used a combination of genomics, epidemiology and ecology to investigate patterns of AMR gene carriage in Escherichia coli, regarded as a sentinel organism.

METHODS

We conducted a structured epidemiological survey of 99 households across Nairobi, Kenya, and whole genome sequenced E. coli isolates from 311 human, 606 livestock and 399 wildlife faecal samples. We used statistical models to investigate the prevalence of AMR carriage and characterise AMR gene diversity and structure of AMR genes in different host populations across the city. We also investigated household-level risk factors for the exchange of AMR genes between sympatric humans and livestock.

RESULTS

We detected 56 unique acquired genes along with 13 point mutations present in variable proportions in human and animal isolates, known to confer resistance to nine antibiotic classes. We find that AMR gene community composition is not associated with host species, but AMR genes were frequently co-located, potentially enabling the acquisition and dispersal of multi-drug resistance in a single step. We find that whilst keeping livestock had no influence on human AMR gene carriage, the potential for AMR transmission across human-livestock interfaces is greatest when manure is poorly disposed of and in larger households.

CONCLUSIONS

Findings of widespread carriage of AMR bacteria in human and animal populations, including in long-distance wildlife species, in community settings highlight the value of evidence-based surveillance to address antimicrobial resistance on a global scale. Our genomic analysis provided an in-depth understanding of AMR determinants at the interfaces of One Health sectors that will inform AMR prevention and control.

Epidemiology of antimicrobial-resistant Escherichia coli carriage in sympatric humans and livestock in a rapidly urbanizing city

There are substantial limitations in understanding of the distribution of antimicrobial resistance (AMR) in humans and livestock in developing countries. This papers present the results of an epidemiological study examining patterns of AMR in Escherichia coli isolates circulating in sympatric human (n = 321) and livestock (n = 633) samples from 99 households across Nairobi, Kenya. E. coli isolates were tested for susceptibility to 13 antimicrobial drugs representing nine antibiotic classes. High rates of AMR were detected, with 47.6% and 21.1% of isolates displaying resistance to three or more and five or more antibiotic classes, respectively. Human isolates showed higher levels of resistance to sulfonamides, trimethoprim, aminoglycosides and penicillins compared with livestock (P<0.01), while poultry isolates were more resistant to tetracyclines (P = 0.01) compared with humans. The most common co-resistant phenotype observed was to tetracyclines, streptomycin and trimethoprim (30.5%). At the household level, AMR carriage in humans was associated with human density (P<0.01) and the presence of livestock manure (P = 0.03), but keeping livestock had no influence on human AMR carriage (P>0.05). These findings revealed a high prevalence of AMR E. coli circulating in healthy humans and livestock in Nairobi, with no evidence to suggest that keeping livestock, when treated as a single risk factor, contributed significantly to the burden of AMR in humans, although the presence of livestock waste was significant. These results provide an understanding of the broader epidemiology of AMR in complex and interconnected urban environments.

Clinically relevant antimicrobial resistance at the wildlife-livestock-human interface in Nairobi: an epidemiological study

BACKGROUND

Antimicrobial resistance is one of the great challenges facing global health security in the modern era. Wildlife, particularly those that use urban environments, are an important but understudied component of epidemiology of antimicrobial resistance. We investigated antimicrobial resistance overlap between sympatric wildlife, humans, livestock, and their shared environment across the developing city of Nairobi, Kenya. We use these data to examine the role of urban wildlife in the spread of clinically relevant antimicrobial resistance.

METHODS

99 households across Nairobi were randomly selected on the basis of socioeconomic stratification. A detailed survey was administered to household occupants, and samples (n=2102) were collected from the faeces of 75 wildlife species inhabiting household compounds (ie, the household and its perimeter; n=849), 13 livestock species (n=656), and humans (n=333), and from the external environment (n=288). Escherichia coli, our sentinel organism, was cultured and a single isolate from each sample tested for sensitivity to 13 antibiotics. Diversity of antimicrobial resistant phenotypes was compared between urban wildlife, humans, livestock, and the environment, to investigate whether wildlife are a net source for antimicrobial resistance in Nairobi. Generalised linear mixed models were used to determine whether the prevalence of antimicrobial resistant phenotypes and multidrug-resistant E coli carriage in urban wildlife is linked to variation in ecological traits, such as foraging behaviour, and to determine household-level risk factors for sharing of antimicrobial resistance between humans, wildlife, and livestock.

FINDINGS

E coli were isolated from 485 samples collected from wildlife between Sept 6,2015, and Sept 28, 2016. Wildlife carried a low prevalence of E coli isolates susceptible to all antibiotics tested (45 [9%] of 485 samples) and a high prevalence of clinically relevant multidrug resistance (252 [52%] of 485 samples), which varied between taxa and by foraging traits. Multiple isolates were resistant to one agent from at least seven antimicrobial classes tested for, and a single isolate was resistant to all antibiotics tested for in the study. The phenotypic diversity of antimicrobial-resistant E coli in wildlife was lower than in livestock, humans, and the environment. Within household compounds, statistical models identified two interfaces for exchange of antimicrobial resistance: between both rodents, humans and their rubbish, and seed-eating birds, humans and their rubbish; and between seed-eating birds, cattle, and bovine manure.

INTERPRETATION

Urban wildlife carry a high burden of clinically relevant antimicrobial-resistant E coli in Nairobi, exhibiting resistance to drugs considered crucial for human medicine by WHO. Identifiable traits of the wildlife contribute to this exposure; however, compared with humans, livestock, and the environment, low phenotypic diversity in wildlife is consistent with the hypothesis that wildlife are a net sink rather than source of clinically relevant resistance. Wildlife that interact closely with humans, livestock, and both human and livestock waste within households, are exposed to more antimicrobial resistant phenotypes, and could therefore act as conduits for the dissemination of clinically relevant antimicrobial resistance to the wider environment. These results provide novel insight into the broader epidemiology of antimicrobial resistance in complex urban environments, characteristic of lower-middle-income countries.

FUNDING

UK Medical Research Council and CGIAR Research Program on Agriculture for Nutrition and Health.

Mapping Nairobi's dairy food system: An essential analysis for policy, industry and research

Demand for dairy products in sub-Saharan Africa, is expected to triple by 2050, while limited increase in supply is predicted. This poses significant food security risk to low income households. Understanding how the dairy food system operates is essential to identify mitigation measures to food insecurity impact. This study aims to determine the structure and functionality of Nairobi's dairy system using a value chain mapping approach. Primary data were gathered through focus group discussions and key informant interviews with dairy value chain stakeholders in Nairobi to obtain qualitative information on people and products in the chains while describing their interactions and flows. Qualitative thematic analysis combined with flowcharts created by participants enabled identification of key food system segments and the development of chain profiles (or flow-diagrams) which together form Nairobi's dairy system. Seven chain profiles forming Nairobi's dairy value chain were identified. These were found to be dominated by small-scale individuals who operate largely independently. Our profiles for the urban and peri-urban farming systems were structurally similar in their downstream networks, obtaining inputs from similar sources. Upstream, the urban systems were shorter, supplying mostly to immediate neighbours or based on own consumption, while the peri urban systems supplied to a wider network and showed some affiliations to producers' associations. Two distinct profiles characterize the milk flow from traders belonging either to a Dairy Traders Association (DTA) or those not belonging to this association (non-DTA). DTA traders sell mainly to fixed retailers and non-DTA traders to mobile retailers (hawkers or roadside vendors). Profiles associated with medium and large cooperatives were driven by networks of collection centres, but with medium-sized cooperatives selling half of their production to large processing companies, and large cooperatives only to fixed retailers. Large processing companies' profiles indicated distribution of high volumes and value addition processing. They reported strategic milk collection arrangements with suppliers on long, medium - or short - term contracts and with well-established product distribution channels. We have identified numerous inter-linkages across dairy chain profiles in Nairobi's complex system, demonstrating significant interdependency among the stakeholders. Therefore, enhancing the system's efficiency requires a holistic, system-wide approach and any policy interventions should consider every segment of the value chain. This study provides a methodological approach for organizations and policy makers to understand and address structural and functional vulnerabilities within food systems more broadly. The insights from this study are relevant to other rapidly growing cities in the region.

A trans-disciplinary study on the health risks of cryptosporidiosis from dairy systems in Dagoretti, Nairobi, Kenya: study background and farming system characteristics

This paper characterises the dairy farming system in Dagoretti, Nairobi. Characterisation was part of a broader ecohealth project to estimate the prevalence and risk of cryptosporidiosis and develop risk mitigation strategies. In the project a trans-disciplinary team addressed epidemiological, socioeconomic, environmental and policy aspects of cryptosporidiosis, an emerging zoonosis. This paper also provides background and describes sampling methods for the wider project. Three hundred dairy households were probabilistically sampled from a sampling frame of all dairy households in five of the six locations of Dagoretti, one of the eight districts of Nairobi Province. Randomly selected households identified 100 non-dairy-keeping households who also took part in the study. A household questionnaire was developed, pre-tested and administered in the dry and wet seasons of 2006. An additional study on livelihood and economic benefits of dairying took place with 100 dairy farmers randomly selected from the 300 farms (as well as 40 non-dairy neighbours as a control group), and a risk-targeted survey of environmental contamination with Cryptosporidium was conducted with 20 farmers randomly selected from the 29 farmers in the wider survey who were considered at high risk because of farming system. We found that around 1 in 80 urban households kept dairy cattle with an average of three cattle per household. Cross-breeds of exotic and local cattle predominate. Heads of dairy-keeping households were significantly less educated than the heads of non-dairy neighbours, had lived in Dagoretti for significantly longer and had significantly larger households. There was a high turnover of 10 % of the cattle population in the 3-month period of the study. Cattle were zero grazed, but productivity parameters were sub-optimal as were hygiene and husbandry practices. In conclusion, dairy keeping is a minor activity in urban Nairobi but important to households involved and their community. Ecohealth approaches are well suited to tackling the complex problem of assessing and managing emerging zoonoses in urban settings.

Outcome mapping for fostering and measuring change in risk management behaviour among urban dairy farmers in Nairobi, Kenya

A study was undertaken to investigate and mitigate the risk from zoonotic Cryptosporidium associated with dairy farming in Dagoretti division, Nairobi, Kenya. Outcome mapping (OM), a relatively new tool for planning and evaluation, was used to foster and then monitor changes in farmer management of health risks. Elements of the OM framework, including the vision, mission and expected progress markers, were developed in participatory sessions and a set of progress markers was used for monitoring behaviour change in farmers participating in the project (the boundary partners). Behaviour change (the outcome challenge) was supported by a range of awareness and educational campaigns, working with strategic partners (extension agents and administrative leaders). The farmers the project worked with made considerable progress according to the markers; they demonstrated an understanding of cryptosporidiosis, established or maintained clean and well drained cattle sheds, and took conscious effort to reduce possible infection. Farmers who did not participate in the project (non-contact farmers) were found to be less advanced on the progress marker indicators. Non-contact farmers who carried out risk-reducing practices had done so independently of the project team. The administration leaders, as strategic partners, had a positive attitude towards the project and confidence in their ability to support project objectives. The study demonstrates the utility of OM in helping to identify and support behavioural change.

Social and gender determinants of risk of cryptosporidiosis, an emerging zoonosis, in Dagoretti, Nairobi, Kenya

The aim of the study was to investigate the social and gender determinants of the risk of exposure to Cryptosporidium from urban dairying in Dagoretti, Nairobi. Focus group discussions were held in six locations to obtain qualitative information on risk of exposure. A repeated cross-sectional descriptive study included participatory assessment and household questionnaires (300 randomly selected urban dairy farming households and 100 non-dairying neighbours). One-hundred dairy households randomly selected from the 300 dairy households participated in an additional economic survey along with 40 neighbouring non-dairy households. We found that exposure to Cryptosporidium was influenced by gender, age and role in the household. Farm workers and people aged 50 to 65 years had most contact with cattle, and women had greater contact with raw milk. However, children had relatively higher consumption of raw milk than other age groups. Adult women had more daily contact with cattle faeces than adult men, and older women had more contact than older men. Employees had greater contact with cattle than other groups and cattle faeces, and most (77 %) were male. Women took more care of sick people and were more at risk from exposure by this route. Poverty did not affect the level of exposure to cattle but did decrease consumption of milk. There was no significant difference between men and women as regards levels of knowledge on symptoms of cryptosporidiosis infections or other zoonotic diseases associated with dairy farming. Awareness of cryptosporidiosis and its transmission increased significantly with rising levels of education. Members of non-dairy households and children under the age of 12 years had significantly higher odds of reporting diarrhoea: gender, season and contact with cattle or cattle dung were not significantly linked with diarrhoea. In conclusion, social and gender factors are important determinants of exposure to zoonotic disease in Nairobi.

Cryptosporidium species detected in calves and cattle in Dagoretti, Nairobi, Kenya

A total of 1,734 cattle faecal samples from 296 dairy-keeping households were collected from urban settings in Nairobi, Kenya. Modified Ziehl-Neelsen staining method and an immunofluorescence assay were used to identify those samples with Cryptosporidium oocyst infection. Oocysts from positive faecal samples were isolated by Sheather's sucrose flotation method and picked from the concentrate using cover slips. Genomic DNA was extracted from 124 of the faecal samples that were positive for Cryptosporidium and was used as template for nested PCR of the 18S rRNA gene. Twenty-five samples (20 %) were PCR-positive for Cryptosporidium, and 24 of the PCR products were successfully cloned and sequenced. Sequence and phylogenetic analysis identified 17 samples (68 %) as Cryptosporidium parvum-like, four samples (16 %) as Cryptosporidium ryanae, three samples (12 %) as Cryptosporidium andersoni and one sample (4 %) as Cryptosporidium hominis. To the best of our knowledge, this is the first genotyping study to report C. parvum-like, C. andersoni and C. hominis in cattle from Kenya. The results of this study show Cryptosporidium infections in calves and cattle may be potential zoonotic reservoirs of the parasite that infects humans.

Aflatoxin B1 and M1 contamination of animal feeds and milk from urban centers in Kenya

BACKGROUND

Aflatoxin M1 (AFM1) is the principal hydroxylated AFB1 metabolite present in milk of cows fed with a diet contaminated with AFB1and excreted within 12 hours of administration of contaminated feeds.

OBJECTIVE

This study was initiated to assess the knowledge and practices of urban dairy farmers and feed millers about aflatoxin in feeds and milk, determine the prevalence and quantify the levels of AFB1 and AFM1 in animal feeds and milk respectively from urban environs in Kenya.

METHODS

This work was carried out in the Department of Public Health Pharmacology and Toxicology, University of Nairobi, Kenya, between February 2006 and March 2007.

RESULTS

A total of 830 animal feed and 613 milk samples from four urban centers were analyzed for aflatoxin B1 and M1 respectively using competitive enzyme immunoassay. Eighty six percent (353/412) of the feed samples from farmers were positive for aflatoxin B1 and 67% (235/353) of these exceeded the FAO/WHO level of 5µ gKg-1. Eighty one percent (197/243) of the feed samples from feed millers and 87% (153/175) from agrochemical shops were positive, while 58% (115/197) and 66% (92/153) of the positive samples exceeded the FAO/WHO limits respectively. Seventy two percent (315/439) of the milk from dairy farmers, 84% (71/85) from large and medium scale farmers and 99% (88/89) of the pasteurized marketed milk were positive for aflatoxin M1, and 20%, 35% an 31% of positive milk from dairy farmers, medium and large scale farmers and market outlets respectively, exceeded the WHO/FAO levels of 0.05µ g/Kg-1. Sixty seven percent of the urban smallholder dairy farmers had no knowledge that milk could be contaminated with aflatoxin M1 and neither knew how they could mitigate against this exposure. Feed millers knew about aflatoxin B1 in grains and excretion of aflatoxin M1 in milk, but were not alleviating exposure to animals.

CONCLUSION

There is need to create awareness and establish routine monitoring of animal feeds and milk to reduce animal and consequently human response.

Overview on urban and peri-urban agriculture: definition, impact on human health, constraints and policy issues

OBJECTIVES

To collate and synthesize current knowledge of components of urban agriculture (UA) with a thematic emphasis on human health impact and a geographic emphasis on East Africa.

DATA SOURCES

Data management followed a structured approach in which key issues were first identified and then studies selected through literature search and personal communication.

DATA EXTRACTION

Evidence-based principles.

DATA SYNTHESIS

Urban agriculture is an important source of food security for urban dwellers in East Africa. Descriptors of UA are location, areas, activities, scale, products, destinations, stakeholders and motivation. Many zoonotic and food-borne diseases have been associated with UA but evidence on human health impact and management is lacking. Major constraints to UA are illegality and lack of access to input and market; policy options have been developed for overcoming these.

CONCLUSION

Urban agriculture is an important activity and likely to remain so. Both positive and negative human health impacts are potentially important but more research is needed to understand these and set appropriate policy and support levels.

Investigations into the prevalence of bovine brucellosis and the risk factors that predispose humans to infection among urban dairy and non-dairy farming households in Dagoretti Division, Nairobi, Kenya

OBJECTIVE

To explore the knowledge, attitudes and practices of dairy and non-dairy farming households in Dagoretti in regard to the risk posed by bovine brucellosis and determine the prevalence of the disease in urban dairy cattle.

DESIGN

A cross sectional study.

SETTING

Urban and Peri-urban dairy farming and non dairy farming households in Dagoretti division, Nairobi.

SUBJECTS

Two hundred ninety nine dairy farming and 149 non dairy farming households.

INTERVENTION

Segregated focus group discussions, administration of a household questionnaire and collection of unboiled milk from dairy and non dairy farming households were the instruments used to gather data on the practices, attitudes, perceptions and prevalence of bovine brucellosis.

RESULTS

Three hundred and ninety three milk samples were collected and analysed for the presence of antibodies to Brucella abortus in an indirect ELISA. The apparent prevalence of bovine brucellosis from milk was estimated at 1% for the samples collected while in dairy farming households the prevalence was 1.1% [0.2, 3.4%] and 0.7% [0.4%] in non dairy farming households.. Thirty percent (90/296) of dairy respondents and 22% (32/147) of non-dairy respondents knew of the existence of brucellosis. Risk of contracting brucellosis was very low considering that milk is boiled together with other ingredients used in making tea and porridge. However, 31% (93/296) and 22% (31/143) of dairy and non dairy farming households respectively made traditionally fermented milk without first boiling the milk. This practice may predispose this group to brucellosis.

CONCLUSION

The low prevalence of bovine brucellosis requires constant surveillance in case the prevalence rates do change. Education of dairy farming households who are more at risk of contracting brucellosis on the transmission pathways and risk factors is required in order to lower further the prevalence of bovine brucellosis in Dagoretti.

Investigation on the prevalence of antimicrobial residues in milk obtained from urban smallholder dairy and non-dairy farming households in Dagoretti Division, Nairobi, Kenya

OBJECTIVES

To assess the prevalence and the level of awareness of the risk posed by antibiotic residues among the urban dairy and non-dairy farming households using a household survey and laboratory analysis of milk samples.

DESIGN

A cross sectional study.

SETTING

Urban small holder dairy farming and non-farming households in Dagoretti division, Nairobi.

RESULTS

The prevalence of antibiotic residues in dairy household milk samples was 4% (11/259) and in milk samples from non-dairy neighbouring households the prevalence was 0.07% (1/136). One sample was detected to belong to beta lactam and one to the tetracycline group of antibiotics. The remaining 10 were not categorised. Approximately 20% of dairy and non-dairy respondents were unsure of the risk that may be posed by the presence of antibiotic residues in milk. A high proportion of the respondents said they would be able to protect themselves from risk posed by antibiotic residues by following advice given by veterinary officers on the withdrawal periods after treatment of animals.

CONCLUSION

Education of the farmers, continuous surveillance and understanding of the socio-economic incentives that would be traded off at farm level would help to reduce or eliminate the risk posed by the residues in marketed or consumed milk.

Investigation into the prevalence of bovine cryptosporidiosis among small-holder dairy households in Dagoretti Division, Nairobi, Kenya

OBJECTIVES

To determine the prevalence of bovine cryptosporidiosis and knowledge of this disease among smallholder dairy households in Dagoretti Division, Nairobi, Kenya.

DESIGN

Cross-sectional survey of 299 dairy households and 149 non-dairy neighbouring households.

SETTING

Dagoretti Division, a mixed urban and peri-urban area of Nairobi.

SUBJECTS

Dairy householders and their immediate, non-cattle keeping neighbours.

RESULTS

There were 50 positive households from 285 households where a fecal sample was collected giving an apparent prevalence of 18% [13, 23]%. Positive households were positively associated with watering cattle with well water, presence of shallow well, cemented cattle shed flooring and number of household cattle. (p < 0.05) Knowledge of cryptosporidiosis was generally low with more dairy respondents, 19% (56/292), who said they had heard of the disease than their non-dairy neighbours, 4% (6/146).

CONCLUSION

This 18% bovine cryptosporidiosis prevalence does not constitute a risk to human health unless Cryptosporidium parvum is present. Typing of these positive samples is needed to assist in accurately determining the risk and enable evidence based management of urban dairy farming.

Prevalence of aflatoxin M1 and B1 in milk and animal feeds from urban smallholder dairy production in Dagoretti Division, Nairobi, Kenya

OBJECTIVE

To estimate the prevalence of Aflatoxin M1 and Total Aflatoxin B1 in milk and animal feeds.

DESIGN

Cross sectional household study.

SETTING

Urban and peri-urban area of Dagoretti Division, Nairobi, Kenya.

SUBJECTS

Two hundred fifty seven dairy farming households and 134 non-dairy neighbouring households.

RESULTS

The prevalence of AFM1 in milk was found to be 45.5% (178/391). The farmer prevalence was 43.5% (112/257), while that of non-farmer was 49.2% (66/ 134). There was however no statistical significant difference between the two categories. Of the 178 positive milk samples, 49% had aflatoxin levels exceeding 0.05 microg Kg(-1). The prevalence of AFB1 in the feed was found to be 98.6% (69/70) with 83% of the samples having aflatoxin B1 levels exceeding 10 microg Kg(-1). Only one feed sample had no traces of AFB1.

CONCLUSION

This study points to an underlying problem that requires the action by policy makers, considering the number of samples with aflatoxin M1 [49%] and aflatoxin B1 [83%] exceeding the WHO/FAO tolerance limits for milk and feeds destined for dairy animals.

Investigation of the prevalence of bovine tuberculosis and risk factors for human infection with bovine tuberculosis among dairy and non-dairy farming neighbour households in Dagoretti Division, Nairobi, Kenya

OBJECTIVE

To determine the prevalence of bovine tuberculosis in urban dairy cattle and examine possible risk factors for human infection with bovine tuberculosis (BTB).

DESIGN

Cross sectional study.

SETTING

Urban and peri-urban dairy and non-dairy farming neighbour households.

SUBJECTS

One hundred forty three dairy cattle and 299 and 149 dairy and non-dairy neighbour households respectively.

RESULTS

Ten percent of the animals (15/143) were found to be reactors to the tuberculin test. The majority of the respondents 57% (168/295) and 72% (106/147) in dairy farming and non-farming households respectively, had limited knowledge of the disease in cattle thus making them unable to adopt any precautionary measures to protect themselves from contracting bovine tuberculosis. Distance from the main house and cattle shed, the time spent attending to the cattle, (on average 4.8 hours), and making of traditionally fermented milk were considered to be the major risk factors.

CONCLUSION

Due to the presumed high background prevalence of human tuberculosis, the specificity of the test employed was unknown. Therefore no definite estimate of the prevalence of BTB was made. It is therefore necessary for further investigation involving culture, isolation and molecular typing from reactors to establish the prevalence of M. bovis in this setting.

Isolation of E. coli O157:H7 from milk and cattle faeces from urban dairy farming and non dairy farming neighbour households in Dagoretti Division, Nairobi, Kenya: prevalence and risk factors

OBJECTIVE

To estimate the prevalence of E. coli O157:H7 in milk and cattle faecal samples dairy and non dairy neighbouring households and to relate this prevalence to the risk to human health.

DESIGN

Cross sectional study.

SETTING

Urban and peri-urban households of Dagoretti, Division, Nairobi, Kenya.

SUBJECTS

Dairy farming households and non dairy farming neighbouring households.

RESULTS

E coli O157:H7 was isolated from milk samples at three of 136 non-dairy neighbour households (2.2% C.I. 0.5%,6.3%) but was not found in any of the milk samples from the 260 milk samples from dairy households (0% C.I. 0.0%,1.4%). E.coli O157:H7 was also found in fifteen of 285 pooled household cattle faecal sample (5.2%, C.I. 3.1%, 8.7%). One of the faecal isolates was found to have the marker for the production of VT1. Discussions with focus groups revealed that the participants had limited knowledge about E. coli O157:H7. Focus group discussions and household questionnaires revealed practices increasing risk of E. coli infections to humans are associated with milking hygiene, drinking water source and treatment, and manure handling.

CONCLUSIONS

E. coli O157:H7 exists in urban setting and continuous surveillance is needed in case conditions and practices change favoring an increase in its prevalence and transmission to people.

Gender, perceptions and behaviour towards health risks associated with urban dairy farming in Dagoretti Division, Nairobi, Kenya

OBJECTIVES

To determine the socio-cultural, economic and environmental factors that encourage urban dairy production and the factors which may predispose the producer, consumer and other handlers to risks associated with dairy farming. To assess the knowledge, attitudes and behaviour of men and women towards health risks and benefits associated with urban dairy farming in smallholder dairy farming and their immediate non-dairy farming neighbour households.

DESIGN

A cross sectional study and participatory urban appraisal (PUA.

SETTING

Urban and peri-urban households in Dagoretti Division, Nairobi.

SUBJECTS

Three hundred dairy farming households, and 150 non-dairy farming neighbour households and six participatory urban appraisals, 58 males and 45 females.

RESULTS

There were more females than males dairy farmers. Both women and men had equal access to resources and benefits obtained from dairy farming but the men had the greater control over the resources. Low levels of knowledge on the specific health risks related to urban dairy farming were observed. Less than half of the respondents believed they were at risk of being exposed to the health hazards, while 63% sensed they could protect themselves from the health risks. There was an association between knowledge levels, perceptions and behaviour of men and women toward risks associated with dairy farming.

CONCLUSIONS

Apart from giving treatment to animals most men did less dairy farming activities. Women rated men lower in all dairy activities but when the men did the scoring for the same activities they rated themselves higher, arguing that their participation was indirect such as providing cash to buy the feed supplements and veterinary services. There were gender differences in all important tasks associated with dairy keeping. Farmers stated that older children, when not in school sometimes assisted but in general children did not show much enthusiasm in dairy work.

Risk of infection with Brucella abortus and Escherichia coli O157:H7 associated with marketing of unpasteurized milk in Kenya

As part of a study to assess zoonotic milk-borne health risks, seasonal survey data and unpasteurized milk samples were collected between January 1999 and February 2000 from randomly selected informal milk market agents (220 and 236 samples in the dry and wet seasons, respectively) and from households purchasing raw milk (213 and 219 samples in the dry and wet seasons, respectively) in rural and urban locations in central Kenya and screened for antibodies to Brucella abortus (B. abortus) and presence of Escherichia coli (E. coli) O157:H7. The latter was assessed based on samples from consumer households only. Antibodies to B. abortus were screened using the indirect antibody Enzyme Linked Immunosorbent Assay (ELISA) and the Milk Ring Test (MRT). The presence of E. coli O157:H7 was assessed by culture, biochemical characterisation, serological testing for production of verocytotoxin one (VT1) and two (VT2) and polymerase chain reaction (PCR) analysis for the presence of genes encoding for the toxins. The prevalence of antibodies to B. abortus varied considerably ranging from none in milk sold in small units and originating from intensive production systems to over 10% in samples that were bulked or originating from extensive production systems. E. coli O157:H7 was isolated from two samples (0.8%), one of which produced VT1. All urban consumers (100%) and nearly all rural consumers (96%) of marketed milk boiled the milk before consumption, mainly in tea, thus greatly reducing chances of exposure to live pathogens and potential health risks.

Control of Taenia saginata by post-mortem examination of carcasses

BACKGROUND

A study to curb transmission cycle of a zoonotic Taenia cestodiasis between humans and cattle is presented.

OBJECTIVE

To evaluate the reliability of meat inspection procedure in detecting carcasses of cattle with T. saginata cysticercosis.

METHODS

A total of 55 cattle divided into two groups of artificially (n=30) and naturally (n= 25) infested animals were utilized. Total dissection method was used as a gold standard of validity.

RESULTS

Meat inspection insensitively revealed cysticerci in 12 carcasses in each group compared with 24 and 23 carcasses revealed by total dissection in natural and artificial infestations, respectively. Sites of oncosphere invasion showed great variations with the two groups of cattle. In the predilection sites, most cysticerci were found in the heart, Triceps brachii, tongue and head muscles in that order. However, non-predilection sites (neck and back, hind limbs, chest, pelvic and lumbar regions, lungs and liver) considerably harboured high numbers of cysticerci. Observations indicated that except for the dead, degenerate or calcified cysticerci a careless meat inspector will 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, becoming the source of bovine cysticercosis.

CONCLUSIONS

The results confirmed that in spite of the time and efforts taken by meat inspectors looking for cysticerci at specified predilection sites of carcasses, this method is insensitive and inaccurate. To effectively improve meat inspection procedures, there is need to increase the area and number of predilection sites observed during inspection and vary them according to the nature of the animals, their husbandry history and the target human population for consumption. In addition, other control approaches such as vaccination, chemotherapy and immunodiagnosis should be developed and implemented to complement meat inspection procedures.

Serodiagnosis of bovine cysticercosis by detecting live Taenia saginata cysts using a monoclonal antibody-based antigen-ELISA

An ante mortem antigen-ELISA-based diagnosis of Taenia saginata cysticercosis was studied in artificially (n = 24) and naturally (n = 25) infected cattle with the objective of further validating the assay as a field diagnostic test. Based on total dissection as the definitive method of validity, the assay minimally detected 14 live cysticerci in artificially infected calves and 2 in naturally infected steers. In natural infections, the minimum number of live cysticerci consistently detected by Ag-ELISA was 5 while in artificial infections it was above 14. However, other animals with 12 and 17 live cysticerci in artificially infected calves, and 1 and 2 live cysticerci in naturally infected steers, escaped detection for unknown reasons. Animals harbouring dead cysticerci gave negative reactions in the assay as was the case in non-infected experimental control calves. There was a statistically significant positive linear correlation between Ag-ELISA optical density values and burdens of live cysticerci as obtained by total dissection of both artificially infected calves (r = 0.798, n = 24; P < 0.05) and naturally infected steers (r = 0.631, n = 25; P < 0.05). These results clearly show the potential effectiveness of ante mortem monoclonal antibody-based antigen detection ELISA in the diagnosis of bovine cysticercosis in cattle. Its value lies in the diagnosis of infection in cattle as a screening test in a herd, rather than as a diagnostic test at the individual level, due to false positive and negative reactions. In a herd of heavily infected cattle, the assay may, however, provide for individual diagnosis. Nevertheless, more work is recommended to increase its sensitivity so as to be able to diagnose light infections consistently in the field.

Caseous lymphadenitis in goats: the pathogenesis, incubation period and serological response after experimental infection

Twenty goats, in two groups of 10, were injected intradermally with Corynebacterium pseudotuberculosis. The doses of infection were 1 x 10(5) and 5 x 10(4) colony-forming units (cfu) for groups 1 and 2, respectively. Thereafter, a goat from each group was killed every 2-3 days and examined for gross and microscopic caseous lesions in the draining lymph nodes. Bands or zones of macrophages and polymorphonuclear granulocytes were observed microscopically on the second day of infection in both groups. Gross caseous lesions were observed from days 8 and 9 of infection, respectively. Positive bacterial agglutination test and haemolysis inhibition test titres were detected after 15-17 days and 20-25 days of infection, respectively. These results indicated that caseous lymphadenitis is a subacute disease with an incubation period of 8-9 days, but that it is not detectable serologically until after 15 days of infection.

Experimental transmission of Besnoitia caprae in goats

Experimental transmission of Besnoitia caprae from naturally chronically-infected goats to susceptible ones was achieved by intra-nasal instillation and intra-conjunctival inoculation of cystozoite-containing suspensions, subcutaneous implantation of fascia containing cysts and alternate needle pricking between the infected and non-infected goats. Typical chronic symptoms developed in the fascia-infected does. Cystozoite inoculation into the eyes and mouth did not result in infection. Kids born of dams with acute and chronic besnoitiosis did not contract the infection in utero, suggesting that intra-uterine transmission may not occur. In contrast to does with acute besnoitiosis, which occasionally aborted, the does with chronic besnoitiosis gave birth to healthy kids. Kids below the age of 4 months (pre-weaned period) born of both infected and non-infected does were susceptible to besnoitiosis but appeared to be more resistant than adult goats.

Prevalence of besnoitiosis in domestic ruminants in Kenya: a preliminary survey

A preliminary survey on the prevalence of besnoitiosis in domestic ruminants in Kenya based on field and farm visits, clinical and post mortem examinations and histopathological examination of tissues and biopsies, showed that goats are the most affected, followed by cattle, while sheep were unaffected. Caprine besnoitiosis occurred in a continuous belt in 5 of the 8 provinces in Kenya stretching from the Coast, Eastern, North Eastern, Nairobi and the Rift Valley Provinces. Mandera, in the North Eastern Province, had the highest prevalence rate of 36%, followed by Kwale (35%), Isiolo (35%), Marsabit (33%), Wajir (28%), Nairobi (26%), Meru (24%), Garissa (21%), Taita Taveta (18%), Embu (17%), Kitui (9%), Machakos (7%), Laikipia (3%), Kajiado (2%) and Turkana and Elgeyo-Marakwet (1% each). In all flocks where the prevalence rates were over 6%, kids were observed to be affected. There were no significant differences (P < 0.05) between the prevalence rates in bucks and does (18% and 18.4, respectively), but kids were less (4%) affected. Bovine besnoitiosis was found only in the Tana River District, with an infection rate of 11%.

Semen characteristics of goats with subacute, acute and chronic besnoitiosis

A study on the semen obtained from breeding goats suffering from mild to severe chronic besnoitiosis revealed marked changes in semen volume, colour, density, concentration, mass and individual motility and percentage live. There were also many neutrophils and spermatozoa with primary and secondary defects, including missing tails and deformed heads and tails. The observed changes were considered to be severe enough to account for the infertility observed in the flock. Sections of testes obtained for histopathology were characterised by massive blockage of the pampiniform plexus, degeneration of the germinal epithelium, tubular necrosis with an inflammatory infiltrate and, in some cases, accumulation of haemosiderin-like material in the tunica vaginalis.

Isolation and characterization of group B streptococci from human and bovine sources within and around Nairobi

Group B streptococci (GBS) were isolated from bovine milk and from vaginas and throats of antenatal and postnatal women using TKT and rapid GBS media. Sixty-three of 529 (12%) bovine bulk milk samples, 9 of 48 (19%) vaginal and 3 of 48 (6%) throat samples were positive. Both bovine and human beta haemolytic isolates were characterized biochemically and serologically. Pigment production was a characteristic of both human and bovine beta haemolytic isolates. The majority (88%) of human isolates fermented salicin and not lactose and most bovine isolates were either lactose positive/salicin positive (41%) or lactose positive/salicin negative (38%). Human and bovine isolates were 100% and 85% typable respectively. Serotype distribution was similar in the bovine and human populations with serotype la, lc and lll being most common in both. Fermentation of sugars showed major differences between bovine and human isolates but similarity in serotype distribution suggests some genetic relationship.

Blood meal sources of Glossina pallidipes and G. longipennis (Diptera: Glossinidae) in Nguruman, southwest Kenya

In total, 1,952 Glossina pallidipes Austen and 1,098 G. longipennis Corti adults were collected in forest and savanna habitat in Nguruman, southwestern Kenya, by NG2G traps during the dry season of 1992. Of these, 339 individuals (11.1%) had blood meals, of which 155 (45.7%) were identified by direct enzyme-linked immunosorbent assay. The most frequent blood meal source was bushbuck, followed by ostrich, elephant, buffalo, and warthog. Few meals were taken from cattle. The findings of frequent blood meals from ostriches is new for G. pallidipes and may indicate that ostriches are an important host. More detailed work on the role of ostriches in the epidemiology of trypanosomiasis is required.

Trials of traps and attractants for Stomoxys spp. (Diptera: Muscidae)

Five blue and black cloth traps designed for tsetse were tested for their ability to catch Stomoxys spp. in Kenya. Significantly greatest catches were obtained with Vavoua traps, which then were used to compare odor baits at Nairobi Park. Acetone, lactic acid, and animal urine (cow, buffalo, waterbuck, camel) or dung (rhinoceros, elephant, hippopotamus) did not increase catches. However, 1-octen-3-ol dispensed at 0.2-2.0 mg/h increased catches up to 3.7-fold. Vavoua traps were highly specific for Stomoxyinae, with 80% of the catch consisting of 11 different taxa of Stomoxys as well as genera such as Prostomoxys, Haematobosca, Stygeromyia, and Rhinomusca. During periods of peak seasonal abundance, up to 3,000 Stomoxys per day were collected in an octenol-baited Vavoua trap. These high catches suggest that Vavoua traps may be of practical use for fly control in isolated settings at a relatively low cost.

Relationships between host blood factors and proteases in Glossina morsitans subspecies infected with Trypanosoma congolense

Host blood effects on Trypanosoma congolense establishment in Glossina morsitans morsitans and Glossina morsitans centralis were investigated using goat, rabbit, cow and rhinoceros blood. Meals containing goat erythrocytes facilitated infection in G.m.morsitans, whereas meals containing goat plasma facilitated infection in G.m.centralis. Goat blood effects were not observed in the presence of complementary rabbit blood components. N-acetyl-glucosamine (a midgut-lectin inhibitor) increased infection rates in some, but not all, blood manipulations. Cholesterol increased infection rates in G.m.centralis only. Both compounds together added to cow blood produced superinfection in G.m.centralis, but not in G.m.morsitans. Midgut protease levels did not differ 6 days post-infection in flies maintaining infections versus flies clearing infections. Protease levels were weakly correlated with patterns of infection, but only in G.m.morsitans. These results suggest that physiological mechanisms responsible for variation in infection rates are only superficially similar in these closely-related tsetse.