Deterministic processes structure bacterial genetic communities across an urban landscape.

Land-use change is predicted to act as a driver of zoonotic disease emergence through human exposure to novel microbial diversity, but evidence for the effects of environmental change on microbial communities in vertebrates is lacking. We sample wild birds at 99 wildlife-livestock-human interfaces across Nairobi, Kenya, and use whole genome sequencing to characterise bacterial genes known to be carried on mobile genetic elements (MGEs) within avian-borne Escherichia coli (n = 241). By modelling the diversity of bacterial genes encoding virulence and antimicrobial resistance (AMR) against ecological and anthropogenic forms of urban environmental change, we demonstrate that communities of avian-borne bacterial genes are shaped by the assemblage of co-existing avian, livestock and human communities, and the habitat within which they exist. In showing that non-random processes structure bacterial genetic communities in urban wildlife, these findings suggest that it should be possible to forecast the effects of urban land-use change on microbial diversity.

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.

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.

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.

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 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 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.

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.

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.

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.

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%.

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.

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.

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.

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.