Prof. S. M. Arimi, born 1949, graduated from the University of Nairobi with a Bachelor of Veterinary Medicine (BVM) in 1976 and subsequently joined the Department of Public Health, Pharmacology and Toxicology on staff development. As part of his Msc. studies, he undertook a postgraduate course in diagnostic microbiology and mastitis diagnostic procedures at the University of Oslo Veterinary School in 1977. In 1979 he graduated from the University of Nairobi with a MSc degree in Public Health (dairy microbiology) and taught food and milk hygiene.

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Mutua, FK, Dewey CE, Arimi' SM, Schelling E, Ogar WO, Levy M.  2011.  Reproductive performance of sows in rural communities of Busia and Kakamega Districts, Western Kenya. Abstract

This study provided baseline performance of breeding pigs information on local sow productivity that was previously lacking. The objective was to investigate performance of breeding pigs in rural smallholder communities of Western Kenya. A random sample of 288 smallholder farms in Busia and Kakamega districts was selected pigs. The farms were visited three times in the course of the study period, 2006 to 2008. Data on management and productivity were gathered by means of questionnaires administered to sow owners. The average number of sows owned per farm was 1.3±0.6. Sows were bred for an average of 2.18±1.08 days during one estrus. Sows were 12.1±4.S months old when they farrowed for the first time. They were bred 1.9±1.6 month after piglets were weaned. Sources of breeding boars included borrowed boars from the neighbourhood (77%), farmers' own boars (14%), group-owned boars (0.4%) and those that were free roaming (2%). The average litter size was 7.8±2.6 while the average number weaned was 6.8±3.1. Piglets were weaned at S.4±3.3 weeks of age. Piglets were reportedly cheaper in Busia (USD 6.36±0.71) than they were in Kakamega (USD 9.71±2.18) (p

Makita, K, Arimi SM, Kang'ethe G;, Mwai CW.  2011.  Risk analysis of E. coli O157: H7 contamination of beef carcasses in slaughter houses in Nairobi, Kenya. Abstract

In the year 2009, a study was carried out in abattoirs supplying meat in Nairobi, Kenya and its environs. Three slaughterhouses with different level of hygiene control, classified as export, improved and typical local, were selected. Three hundred cattle were tracked along the slaughtering process to sample faeces and carcass swabs. Faecal samples from the rectum were taken from each animal after stunning. Two carcass sites, flank and brisket were swabbed after flaying, evisceration and after cleaning. In total seven samples were taken from each carcass. METHODS: E.coli O157 was isolated by culture and serotyped using card agglutination test. The isolates were further tested for verotoxin production and Monte Carlo simulation was run to determine the risk of carcass contamination. A HACCP model was also developed for one of the abattoirs. E.coli O157:H7 was detected from the faecal and carcasses samples at different stages. RESULTS: Two hundred and eighty out of 2,100 samples (13.3%) were IMVIC positive for E. coli. (++---) and Sorbitol MacConkey negative and were therefore tentative E. coli O157 colonies. After serotyping for O157, 92 out of 280 (4.3%) isolates, were positive for E. coli O157:H7. Forty two isolates were tested for verotoxin production, eight were positive for VT1 only while two were positive for both VT1 and VT2. The probability of a carcass being contaminated with E.coli O157 in the abattoir was 2.9% (90% CI: 0.8%-6.1%), 4.8% (90%CI: 2.0%-8.6%) and 3.8% (90%CI: 1.3%-7.3%) in the export, the local improved and the typical local abattoir respectively. Based on E. coli detection as an indicator of hygiene, the risk of contamination is low in the export slaughter house followed by the typical local slaughter house and highest in the local improved; however the confidence intervals overlapped and the level of hygiene was not significantly different. This trend was observed also for the probability of a carcasses being contaminated with vero-toxin producing E. coli: 0.7% (90% CI: 0.2%-1.7%), 1.2% (90% CI: 0.4%-2.4%) and 1.0% (90% CI: 0.3%-2.0%) in the export, the local improved and the typical local abattoir, respectively. SUMMARY: This study shows that there is a risk of carcass contamination with E.coli O157 in all the different categories of slaughterhouses in Nairobi.


Arimi, SM, Koroti E, Kangethe EK;, Omore AO;, McDermott JJ.  2005.  Risk of infection with Brucella abortus and Escherichia coli 0157:H7 associated with marketing of unpasteurized milk in Kenya. Abstract

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) OI57: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 0157:H7 was assessed by culture, biochemical characterisation, serological testing for production of verocytotoxin one (VTl) and two (VT2) and polymerase chain reaction (Pf.R) 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 0157:H7 was isolated from two samples (0.8%), one of which produced VTl. 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.



Arimi, SM;, Koroti E;, Kang'ethe EK;, Omore AO;, McDermott JJ;, Macharia JK;, Nduhiu JG;, Githua AM.  2000.  Risk of infection from E. coli O157: H7 through informally marketed raw milk in Kenya. Abstract

E. coli 0157:H7 is a newly recognised bacterial zoonosis that originates from the gut of infected cattle. It causes potentially fatal haemorrhagic enteritis, haemolytic uraemic syndrome and kidney damage in humans. Epidemiological data on E. coli 0157:H7 infection and transmission in developing countries remain scarce but it is suspected that consumption of unpasteurised milk is an important vehicle for its transmission to humans, as milk can easily be contaminated with cattle faeces during milking. Given the high proportion of informal sales of unpasteurized milk in many tropical countries, E. coli 0157:H7 has been one of several zoonoses of concern. Between January 1999 and January 2000, survey data and raw milk samples were collected seasonally from households consuming unpasteurised milk in rural and urban locations in central Kenya. Respondents were randomly selected within production system (extensive and intensive) and human population density (urban, peri-urban and rural) strata. Laboratory samples were assessed for bacteriological quality by total and coliform counts. Selective media were used sequentially to screen for faecal coliforms and E. coli 0157:H7. Suspect E. coli 0157:H7 colonies were also serotyped and tested for production of verocytotoxins. E. coli was recovered from 91 out of 264 samples (34%) and E. coli 0157:H7 serotype identified in two samples (<1%). One of the two isolates produced verocytotoxins. As in many studies, the recovery rate of this serotype was low, but the finding is significant from a public health perspective. Our consumer studies have shown that over 95% of consumers of unpasteurised milk boil the milk before consumption and potential health risks from this zoonosis are therefore quite low. As informal milk markets without pasteurisation technology are likely to remain dominant for the foreseeable future, there is the need to further emphasise the importance of boiling raw milk before consumption, especially among pastoral communities where this practice is not common.

Aboge, GO;, Kang’ethe EK;, Arimi SM;, Omore AO;, McDermott JJ;, Kanja LW;, Macharia JK;, Nduhiu JG;, Githua A.  2000.  Antimicrobial Agents Detected In Marketed Milk In Kenya. Abstract

Drug residues in foods are a major public health concern in many countries, especially where most food sales bypass official quality assurance channels. In common with many tropical countries, sales of unpasteurized milk in Kenya account for over 85% of marketed milk. This milk is either sold directly from producers to consumers or via various cadres of informal market agents. Besides residues that may arise from lack of adherence to withdrawal times following cow therapy, there have been concerns that some antimicrobial agents may be added to informally marketed milk to extend its shelf life. As part of a large study to assess public health hazards associated with marketed milk, samples were collected seasonally between January 1999 and January 2000 from raw (unpasteurized) milk consuming households and informal market agents of various cadres. Pasteurised milk samples were also collected from retail points and tested for comparison. All samples were screened for antimicrobial residues using charm AIM-96 and Charm-ROSA (Charm Sciences Inc, USA) tests. The former detects a wide range of anti-microbials, and the latter detects β-lactams and tetracyclines specifically, at levels above maximum residue limits (MRLS) recommended by the European Union (EU). The Charm-AIM screening test showed that 9.4% and 5.7% of samples from consumer households and market agents had antimicrobial residues above EU MRLS, respectively. It was concluded that antimicrobial residues were more likely to have originated at farm-level than because of poor market handling practices.

Mwangi, A, Arimi SM, Mbugua S, Kang'ethe EK.  2000.  Resource Management and Agricultural Technology.
Muriuki, SM, Mugambi TJ, Gathura PB, Arimi SM, McDermott JJ, Maichomo MW.  2000.  Study of brucellosis in a pastoral community and evaluation of the usefulness of clinical signs and symptoms in differentiating it from other flu-like diseases. Abstract

A study of differentials causing flu-like symptoms (malaria, typhoid, streptococcal infections and rheumatoid arthritis) in 488 patients from a pastoralist area is presented. The potential usefulness of clinical signs, symptoms and diagnostic tests in ruling-in or ruling-out these diseases was investigated in the District hospital and three outlying health dispensaries. For each patient a detailed clinical history plus diagnostic test for brucellosis, typhoid, streptococcal infections and rheumatoid arthritis, and for some patients malaria were conducted. Incidence levels of these diseases were estimated using laboratory test results; brucellosis, 13%, typhoid, 40%: streptococcal infections, 6% malaria, 9%: and rheumatoid arthritis, 10%. Brucellosis could not be differentiated clinically from the other flu-like diseases but rheumatoid arthritis could.


Osano, O, Arimi SM.  1999.  Retail poultry and beef as sources of campylobacter jejuni. Abstract

Objectives: To investigate the level of contamination with C. jejuni of raw chicken and beef meats sold in Nairobi and to assess their potential as sources of campylobacter infections to man. Design: Dressed chicken and beef meat samples were randomly sourced from butcheries, markets and supermarkets in various parts of Nairobi over a period of two months. One hundred chicken and 50 beef samples were bacteriologically examined by selective enrichment and culture under microaerophilic environment. Thermophilic campylobacters were identified and characterised using standard physical and biochemical tests. Setting: Veterinary Public Health Laboratories, Kabete, University of Nairobi. Results: Thermophilic campylobacters were isolated from 77 (77%) poultry samples and one (2 %) beef sample. Isolation rate (85.3 %) was higher from chickens <24 hours old since slaughter than those >24 hours old. The beef isolate was 2% C. jejuni. Poultry samples yielded C. jejuni (59%), C. coli (39% and C. laridis (2%). Conclusion: These findings show that poultry meat sold at the counter is a major source of C. jejuni and C. coli, and that it is an important potential source of campylobacter infection. Proper cooking and hygienic handling before consumption is therefore essential.



E T, R, Arimi SM, C W D.  1997.  Effects of pH on distribution of Listeria ribotypes in corn, hay, and grass silage.. Abstract

Listeria app, isolated from 13 of 129 (10%) corn silage samples, 21 of 76 (28%) hay silage samples, and 3 of 5 (60%) grass silage samples during a previous Vermont survey were subjected to automated ribotype (RT) analysis. The 13 positive corn silage samples contained 3 Listeria monocytogenes isolated (three RTs, including one known clinical RT) and 10 L. innocua isolates (four RTs). Similarly, 2 L. monocytogenes isolates (two RTs) and 19 L. innocua isolates (three RTs) were identified in the 21 positive hay silage samples. The three positive grass silage samples contained two L. innocua isolates (two RTs) and one isolate of L. welshimeri. One hundred seven of 129 (83%) high-quality (pH < 4.0) corn silage samples accounted for 8 of 13 Listeria isolates from corn silage, including isolates belonging to one L. monocytogenes clinical RT. In contrast, low-quality hay silage (70 of 76 [92%] samples having a pH of > or = 4.0) harbored 20 of 21 isolates, including isolates belonging to two nonclinical L. monocytogenes RTs. Poor-quality silage is readily discernible by appearance; however, these findings raise new concerns regarding the safety of high-quality (pH < 4.0) corn silage, which can contain Listeria spp., including L. monocytogenes strains belonging to RTs of clinical importance in cases of food-borne listeriosis.


Ryser, ET, Arimi SM, Bunduki MM, Donnelly CW.  1996.  Recovery of different Listeria ribotypes from naturally contaminated, raw refrigerated meat and poultry products with two primary enrichment media.. Abstract

Isolation rates for Listeria monocytogenes and the other Listeria spp. typically improve when samples are enriched in more than one primary enrichment medium. This study evaluated the abilities of two primary enrichment media, University of Vermont-modified Listeria enrichment broth (UVM) and Listeria repair broth (LRB), to recover different ribotypes of Listeria spp. from raw meat and poultry samples. Forty-five paired 25-g retail samples of ground beef, pork sausage, ground turkey, and chicken (160 samples) underwent primary enrichment in UVM and LRB (30 degrees C for 24 h) followed by secondary enrichment in Fraser broth (35 degrees C for 24 and 40 h) and plating on modified Oxford agar. After 24 h of incubation of 35 degrees C, 608 Listeria colonies from selected positive samples were biochemically confirmed as L. monocytogenes (245 isolates), L innocua (276 isolates), and L. welshimeri (89 isolates) and then ribotyped with the automated Riboprinter microbial characterization system (E. I. du Pont de Nemours & Co., Inc.). Thirty-six different Listeria strains comprising 16 L. monocytogenes (including four known clinical ribotypes), 12 L. innocua, and 8 L. welshimeri ribotypes were identified from selected positive samples (15 samples of each product type; two UVM and two LRB isolates per sample). Twenty-six of 36(13 L. monocytogenes) ribotypes were detected with both UVM and LRB, whereas 3 of 36 (1 L. monocytogenes) and 7 of 36 (3 L. monocytogenes) Listeria ribotypes were observed with only UVM or LRB, respectively. Ground beef, pork sausage, ground turkey, and chicken yielded 22 (8 L. monocytogenes), 21 (12 L. monocytogenes), 20 (9 L. monocytogenes), and 19 (11 L. monocytogenes) different Listeria ribotypes, respectively, with some Listeria ribotypes confined to a particular product. More importantly, major differences in both the number and distribution of Listeria ribotypes, including previously recognized clinical and nonclinical ribotypes of L. monocytogenes, were observed when 10 UVM and 10 LRB isolates from five samples of each product were ribotyped. When a third set of six samples per product type was examined from which two Listeria isolates were obtained by using only one of the two primary enrichment media, UVM and LRB failed to detect L. monocytogenes (both clinical and nonclinical ribotypes) in two and four samples, respectively. These findings stress the importance of using more than one primary enrichment medium and picking a sufficient number of colonies per sample when attempting to isolate specific L. monocytogenes strains during investigations of food-borne listeriosis.


Ombui, JN, McDermott JJ, Arimi SM.  1995.  The role of dairy cooperative societies in providing services to small-holder dairy farmers in Kiambu district, Kenya. Abstract

A study on the role of dairy cooperative societies in providing services to small-holder dairy farmers in Kiambu district, Kenya, was carried out through interview to staff from various cooperative societies and farmers. The prices paid to farmers varied from Ksh. 5.00 to Ksh. 7.00 per litre and was influenced mostly by the proportion of milk the cooperative society was able to sell locally. The ability of the societies to provide input services increased with the number of members and the amount of cooperative levy charged on milk sales. The need for higher and more prompt payment for milk was a major concern to farmers while the provision of veterinary services was a secondary concern. It is concluded that both the recent deregulation of milk marketing and the withdrawal of many government technical services should influence dairy cooperative societies to assume a greater role in their areas.



Ombui, JN, Arimi SM, Kayihura M.  1992.  Raw milk as a source of enterotoxigenic Staphylococcus aureus and enterotoxins in consumer milk.. Abstract

Staphylococcus aureus strains were isolated from 183 of 300 raw milk samples collected at the Kenya Co-operative Creamery (Dandora). 97 of these 183 trains were assayed for the production of enterotoxin A, B, C and D. Seventy two (74.2%) of these were found to produce either a single or a combination of enterotoxins. Raw milk is a potential source of enterotoxigenic S. aureus in milk and milk products, especially if there is defective pasteurisation.


Arimi, SM, Fricker CR, Park RWA.  1990.  Study of haemolytic activity of some Campylobacter spp. on blood agar plates. Abstract

A total of 152 strains of Campylobacter jejuni, C. coli, C. laridis and C. fetus subsp. fetus were tested for haemolysis on blood agar plates. Distinct haemolysis was detected in 92.% (96/104) of strains of C. jejuni and 21.7% (5/23) of strains of C. coli on sheep blood heart infusion agar after incubation for 4 d microacrobically at 42°C. Haemolysis was also detected on horse blood heart infusion agar. Haemolysis was not detected at 37°C except with one of 50 strains of C. jejuni tested at this temperature, which was weakly positive. Campylobacter laridis was not haemolytic; C. fetus subsp. fetus, which does not grow at 42°C, showed no haemolysis at 37°C. Blood agar (Oxoid, BA Base No. 2) was not suitable for testing for haemolysis by these organisms. A microaerobic gas mixture containing hydrogen is better than that containing nitrogen because the medium has a brighter colour, making haemolysis casier to detect. There was no synergistic haemolysis with Staphylococcus aureus or Streptococcus agalactiae. The plate haemolysis test as described here may aid differentiation within the thermophilic campylobacters



Lindqvist, KJ, Arimi SM, Kaburia HFA, Kayihura M.  1987.  Staphylococcal enterotoxin Ä in raw and pasteurized milk.

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