Validation of the bag-mediated filtration system for environmental surveillance of poliovirus in Nairobi, Kenya.

AIMS: This study compared the bag-mediated filtration system (BMFS) and standard WHO two-phase separation methods for poliovirus (PV) environmental surveillance, examined factors impacting PV detection and monitored Sabin-like (SL) PV type 2 presence with withdrawal of oral polio vaccine type 2 (OPV2) in April 2016. METHODS AND RESULTS: Environmental samples were collected in Nairobi, Kenya (Sept 2015-Feb 2017), concentrated via BMFS and two-phase separation methods, then assayed using the WHO PV isolation algorithm and intratypic differentiation diagnostic screening kit. SL1, SL2 and SL3 were detected at higher rates in BMFS than two-phase samples (P < 0·05). In BMFS samples, SL PV detection did not significantly differ with volume filtered, filtration time or filter shipment time (P > 0·05), while SL3 was detected less frequently with higher shipment temperatures (P = 0·027). SL2 was detected more frequently before OPV2 withdrawal in BMFS and two-phase samples (P < 1 × 10-5 ). CONCLUSIONS: Poliovirus was detected at higher rates with the BMFS, a method that includes a secondary concentration step, than using the standard WHO two-phase method. SL2 disappearance from the environment was commensurate with OPV2 withdrawal. SIGNIFICANCE AND IMPACT OF THE STUDY: The BMFS offers comparable or improved PV detection under the conditions in this study, relative to the two-phase method.

Rabies: the emergence of a microbial threat.

Since 1912 when rabies was first confirmed in Kenya, the disease has largely existed in varying degrees of occurrence. Spatial and temporal distribution of cases of animal rabies are well documented. Records of human cases have not been as detailed as the veterinary cases. The principal animal reservoir for rabies has been the dog. Save for the 1960s, rabies outbreaks occurred in the country for most part of this century. The 1980's witnessed a dramatic upward swing in the number of cases reported annually. Over the years an enzootic pattern covering most parts of the country emerged. This article reviews available data showing rabies as an emerging microbial threat in Kenya.

Missed opportunities and inappropriately given vaccines reduce immunisation coverage in facilities that serve slum areas of Nairobi.

OBJECTIVES: To quantify missed opportunities for immunisation, document reasons for their occurrence and evaluate the extent of inappropriately given vaccine doses. DESIGN: A cross sectional study of children under two years of age attending health facilities. SETTING: Six health facilities predominantly serving the slums of Nairobi. METHODOLOGY: Information on vaccination was extracted from child immunisation cards as well as from mothers or guardians of children. RESULTS: Effective immunisation coverage for Bacille-Callmette Guerin (BCG) was 91%. Coverage for the birth dose, first, second, and third doses of oral polio vaccine (OPV0, OPVI, OPV2, and OPV3) was 44%, 83%, 79% and 75% respectively. Effective coverage for first, second and third doses of diphtheria-pertusis-tetanus (DPTI, DPT2 and DPT3) vaccine was 88%, 87% and 85% respectively. Measles coverage was 80%. Immunisation coverage for all antigens except OPV0 and OPV3 would have been increased to over 90% had missed immunisation opportunities and inappropriately administered vaccination been avoided. There would have been an 11% increase in OPV3 coverage to 86%. Increases in coverage for OPVI and OPV2 would have been 16% and 18% respectively. Coverage would have increased by 10% for diphtheria pertusistetanus (DPT) doses DPTI and DPT2, and 7% for DPT3. Measles immunisation coverage would have increased by 19% had missed immunisation opportunities and inappropriately administered vaccinations been avoided. The overall missed opportunities rate was 3%. The proportions of missed opportunities were higher for the OPV series than DPT series. CONCLUSION: Missed immunisation opportunities among clinic attendees in Nairobi occur and routine supervision should be strengthened in these health facilities in order to minimise such missed opportunities and inappropriately administered vaccines.

Measles trends and vaccine effectiveness in Nairobi, Kenya.

OBJECTIVES: To determine morbidity and mortality from measles and to estimate measles vaccine effectiveness among children hospitalised with measles in two hospitals in Nairobi. DESIGN: A review of hospital records (index cards). SETTING: Kenyatta National Hospital and Mbagathi District Hospitals covering the years 1996-2000. METHOD: A review of index cards for measles morbility and mortality was undertaken in the two hospitals. Measles data at the Kenya Expanded Programme on Immunisation covering both hospitals was analysed for vaccine effectiveness. RESULTS: The incidence of measles was unusually high in 1998 between July and November (monthly range 130-305), reflecting on the occurrence of an outbreak at that time. There was no definite monthly incidence trend of measles in 1996,1997, 1999 and 2000. The median age of cases was 13 months (range 0-420 months) for Kenyatta hospital and 18 months (range 1-336 months) for Mbagathi Hospital. Significantly, 29.8% of all cases were aged below nine months when routine immunisation for measles had not begun. The median number of days spent in hospital were five days (range 0-87 days) for Kenyatta and four days (range 1-13 days) for Mbagathi. The overall case fatality rate was 5.6% and was similar for both males and females. The overall measles vaccine effectiveness among measles cases admitted to Kenyatta and Mbagathi Hospitals was 84.1%. CONCLUSION: The case admissions in Kenyatta and Mbagathi Hospitals suggest measles was prevalent in Nairobi over the latter half decade of the 1990's. Apart from 1998 when there was an outbreak, the seasonality of measles was dampened. The 1998 outbreak suggests a build up of susceptible children the majority of whom were born in the last quarter of 1996. The high mortality may have had to do with the majority of cases presenting late when symptoms were already complicated and severe.

Schistosoma mansoni in the baboon: modulation of pathology after vaccination with polyclonal anti-idiotypic antibodies.

Vaccination of five baboons with an anti-idiotypic vaccine to irradiated Schistosoma mansoni cercariae resulted in nearly 19% protection compared to 39% protection conferred to five baboons vaccinated with an irradiated vaccine. Vaccination with the anti-idiotypic antibodies resulted in a significant reduction of pathology and granuloma size following challenge with live unattenuated cercariae. Results presented in this work are considered highly significant because the anti-idiotypic vaccine markedly influenced schistosomiasis morbidity which is the main consideration in this disease.

Yellow fever in Kenya: the need for a country-wide surveillance programme.

Since the emergence of yellow fever (YF) as a public health threat in Kenya in 1992-1993, low level transmission of the virus to humans has continued to occur. A programme of YF surveillance has been instrumental in the monitoring of YF activity and has clearly demonstrated an expansion of the zone of virus activity into regions that were not affected in the 1992-1993 epidemic. This is of major concern for the approximately 29 million Kenyans who are unvaccinated and therefore at risk of infection. A revision of the surveillance programme is underway to create a more efficient system of recognition of suspect YF cases, laboratory diagnosis and reporting to the appropriate authorities for action. In addition, a research programme to study YF ecology in Kenya will benefit the surveillance programme, enabling it to target potential 'hotspots' of YF activity. As it may not be possible, for financial reasons, to incorporate YF vaccination into the Kenya Expanded Programme of immunization in the immediate future, the need for continued surveillance to monitor the emergence of YF in Kenya is vital.