Last data update: Sep 16, 2024. (Total: 47680 publications since 2009)
Records 1-9 (of 9 Records) |
Query Trace: Nderitu L [original query] |
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Spatial clustering of livestock Anthrax events associated with agro-ecological zones in Kenya, 1957-2017
Nderitu LM , Gachohi J , Otieno F , Mogoa EG , Muturi M , Mwatondo A , Osoro EM , Ngere I , Munyua PM , Oyas H , Njagi O , Lofgren E , Marsh T , Widdowson MA , Bett B , Njenga MK . BMC Infect Dis 2021 21 (1) 191 BACKGROUND: Developing disease risk maps for priority endemic and episodic diseases is becoming increasingly important for more effective disease management, particularly in resource limited countries. For endemic and easily diagnosed diseases such as anthrax, using historical data to identify hotspots and start to define ecological risk factors of its occurrence is a plausible approach. Using 666 livestock anthrax events reported in Kenya over 60 years (1957-2017), we determined the temporal and spatial patterns of the disease as a step towards identifying and characterizing anthrax hotspots in the region. METHODS: Data were initially aggregated by administrative unit and later analyzed by agro-ecological zones (AEZ) to reveal anthrax spatio-temporal trends and patterns. Variations in the occurrence of anthrax events were estimated by fitting Poisson generalized linear mixed-effects models to the data with AEZs and calendar months as fixed effects and sub-counties as random effects. RESULTS: The country reported approximately 10 anthrax events annually, with the number increasing to as many as 50 annually by the year 2005. Spatial classification of the events in eight counties that reported the highest numbers revealed spatial clustering in certain administrative sub-counties, with 12% of the sub-counties responsible for over 30% of anthrax events, whereas 36% did not report any anthrax disease over the 60-year period. When segregated by AEZs, there was significantly greater risk of anthrax disease occurring in agro-alpine, high, and medium potential AEZs when compared to the agriculturally low potential arid and semi-arid AEZs of the country (p < 0.05). Interestingly, cattle were > 10 times more likely to be infected by B. anthracis than sheep, goats, or camels. There was lower risk of anthrax events in August (P = 0.034) and December (P = 0.061), months that follow long and short rain periods, respectively. CONCLUSION: Taken together, these findings suggest existence of certain geographic, ecological, and demographic risk factors that promote B. anthracis persistence and trasmission in the disease hotspots. |
Temporal and spatial distribution of anthrax outbreaks among Kenyan wildlife, 1999–2017
Gachohi JM , Gakuya F , Lekolool I , Osoro E , Nderitu L , Munyua P , Ngere I , Kemunto N , Bett B , Otieno F , Muturi M , Mwatondo A , Widdowson MA , Kariuki Njenga M . Epidemiol Infect 2019 147 The burden of anthrax in wildlife is demonstrated through high numbers of sudden mortalities among herbivore species, including endangered animal species. East Africa is home of multiple species of faunal wildlife numbering in the millions but there are limited disease surveillance programmes, resulting in a paucity of information on the role of anthrax and other infectious diseases on declining wildlife populations in the region. We reviewed historical data on anthrax outbreaks from Kenya Wildlife Service (KWS) spanning from 1999 to 2017 in Kenya to determine the burden, characteristics and spatial distribution of anthrax outbreaks. A total of 51 anthrax outbreaks associated with 1014 animal deaths were reported across 20 of 60 wildlife conservation areas located in six of the seven agro-ecological zones. Overall, 67% of the outbreaks were reported during the dry seasons, affecting 24 different wildlife species. Over 90% (22 of 24) of the affected species were herbivore, including 12 grazers, five browsers and five mixed grazers and browsers. Buffaloes (23.5%), black rhinos (21.6%) and elephants (17.6%) were the most frequently affected species. Our findings demonstrate the extensive geographic distribution of wildlife anthrax in the country, making it one of the important infectious diseases that threaten wildlife conservation. |
Temporal and spatial distribution of anthrax outbreaks among Kenyan wildlife, 19992017
Gachohi JM , Gakuya F , Lekolool I , Osoro E , Nderitu L , Munyua P , Ngere I , Kemunto N , Bett B , Otieno F , Muturi M , Mwatondo A , Widdowson MA , KariukiNjenga M . Epidemiol Infect 2019 147 The burden of anthrax in wildlife is demonstrated through high numbers of sudden mortalities among herbivore species, including endangered animal species. East Africa is home of multiple species of faunal wildlife numbering in the millions but there are limited disease surveillance programmes, resulting in a paucity of information on the role of anthrax and other infectious diseases on declining wildlife populations in the region. We reviewed historical data on anthrax outbreaks from Kenya Wildlife Service (KWS) spanning from 1999 to 2017 in Kenya to determine the burden, characteristics and spatial distribution of anthrax outbreaks. A total of 51 anthrax outbreaks associated with 1014 animal deaths were reported across 20 of 60 wildlife conservation areas located in six of the seven agro-ecological zones. Overall, 67% of the outbreaks were reported during the dry seasons, affecting 24 different wildlife species. Over 90% (22 of 24) of the affected species were herbivore, including 12 grazers, five browsers and five mixed grazers and browsers. Buffaloes (23.5%), black rhinos (21.6%) and elephants (17.6%) were the most frequently affected species. Our findings demonstrate the extensive geographic distribution of wildlife anthrax in the country, making it one of the important infectious diseases that threaten wildlife conservation. |
Seroprevalence of infections with dengue, Rift Valley fever and chikungunya viruses in Kenya, 2007
Ochieng C , Ahenda P , Vittor AY , Nyoka R , Gikunju S , Wachira C , Waiboci L , Umuro M , Kim AA , Nderitu L , Juma B , Montgomery JM , Breiman RF , Fields B . PLoS One 2015 10 (7) e0132645 Arthropod-borne viruses are a major constituent of emerging infectious diseases worldwide, but limited data are available on the prevalence, distribution, and risk factors for transmission in Kenya and East Africa. In this study, we used 1,091 HIV-negative blood specimens from the 2007 Kenya AIDS Indicator Survey (KAIS 2007) to test for the presence of IgG antibodies to dengue virus (DENV), chikungunya virus (CHIKV) and Rift Valley fever virus (RVFV).The KAIS 2007 was a national population-based survey conducted by the Government of Kenya to provide comprehensive information needed to address the HIV/AIDS epidemic. Antibody testing for arboviruses was performed on stored blood specimens from KAIS 2007 through a two-step sandwich IgG ELISA using either commercially available kits or CDC-developed assays. Out of the 1,091 samples tested, 210 (19.2%) were positive for IgG antibodies against at least one of the three arboviruses. DENV was the most common of the three viruses tested (12.5% positive), followed by RVFV and CHIKV (4.5% and 0.97%, respectively). For DENV and RVFV, the participant's province of residence was significantly associated (P≤.01) with seropositivity. Seroprevalence of DENV and RVFV increased with age, while there was no correlation between province of residence/age and seropositivity for CHIKV. Females had twelve times higher odds of exposure to CHIK as opposed to DENV and RVFV where both males and females had the same odds of exposure. Lack of education was significantly associated with a higher odds of previous infection with either DENV or RVFV (p <0.01). These data show that a number of people are at risk of arbovirus infections depending on their geographic location in Kenya and transmission of these pathogens is greater than previously appreciated. This poses a public health risk, especially for DENV. |
Hepatitis E outbreak, Dadaab refugee camp, Kenya, 2012
Ahmed JA , Moturi E , Spiegel P , Schilperoord M , Burton W , Kassim NH , Mohamed A , Ochieng M , Nderitu L , Navarro-Colorado C , Burke H , Cookson S , Handzel T , Waiboci LW , Montgomery JM , Teshale E , Marano N . Emerg Infect Dis 2013 19 (6) 1010-1 Hepatitis E virus (HEV) is transmitted through the fecal-oral route and is a common cause of viral hepatitis in developing countries. HEV outbreaks have been documented among forcibly displaced persons living in camps in East Africa, but for >10 years, no cases were documented among Somali refugees (1,2). On August 15, 2012, the US Centers for Disease Control and Prevention (CDC) in Nairobi, Kenya, was notified of a cluster of acute jaundice syndrome (AJS) cases in refugee camps in Dadaab, Kenya. On September 5, a CDC epidemiologist assisted the United Nations High Commissioner for Refugees (UNHCR) and its partners in assessing AJS case-patients in the camp, enhancing surveillance, and improving medical management of case-patients. We present the epidemiologic and laboratory findings for the AJS cases (defined as acute onset of scleral icterus not due to another underlying condition) identified during this outbreak. | Dadaab refugee camp is located in eastern Kenya near the border with Somalia. It has existed since 1991 and is the largest refugee camp in the world. Dadaab is composed of 5 smaller camps: Dagahaley, Hagadera, Ifo, Ifo II, and Kambioos. As of December 2012, a total of 460,000 refugees, mainly Somalians, were living in the camps; >25% were recent arrivals displaced by the mid-2011 famine in the Horn of Africa (3). Overcrowding and poor sanitation have led to outbreaks of enteric diseases, including cholera and shigellosis (4); in September 2012, an outbreak of cholera occurred simultaneously with the AJS outbreak. |
Association of the CT values of real-time PCR of viral upper respiratory tract infection with clinical severity, Kenya
Fuller JA , Njenga MK , Bigogo G , Aura B , Ope MO , Nderitu L , Wakhule L , Erdman DD , Breiman RF , Feikin DR . J Med Virol 2013 85 (5) 924-32 Quantitative real-time polymerase chain reaction (qRT-PCR) assay of the upper respiratory tract is used increasingly to diagnose lower respiratory tract infections. The cycle threshold (CT) values of qRT-PCR are continuous, semi-quantitative measurements of viral load, although interpretation of diagnostic qRT-PCR results are often categorized as positive, indeterminate, or negative, obscuring potentially useful clinical interpretation of CT values. From 2008 to 2010, naso/oropharyngeal swabs were collected from outpatients with influenza-like illness, inpatients with severe respiratory illness, and asymptomatic controls in rural Kenya. CT values of positive specimens (i.e., CT values < 40.0) were compared by clinical severity category for five viruses using Mann-Whitney U-test and logistic regression. Among children <5 years old we tested with respiratory syncytial virus (RSV), inpatients had lower median CT values (27.2) than controls (35.8, P = 0.008) and outpatients (34.7, P < 0.001). Among children and older patients infected with influenza virus, outpatients had the lowest median CT values (29.8 and 24.1, respectively) compared with controls (P = 0.193 for children, P < 0.001 for older participants) and inpatients (P = 0.009 for children, P < 0.001 for older participants). All differences remained significant in logistic regression when controlling for age, days since onset, and coinfection. CT values were similar for adenovirus, human metapneumovirus, and parainfluenza virus in all severity groups. In conclusion, the CT values from the qRT-PCR of upper respiratory tract specimens were associated with clinical severity for some respiratory viruses. (J. Med. Virol. 85:924-932, 2013. (c) 2013 Wiley Periodicals, Inc.) |
Etiology and incidence of viral and bacterial acute respiratory illness among older children and adults in rural western Kenya, 2007-2010
Feikin DR , Njenga MK , Bigogo G , Aura B , Aol G , Audi A , Jagero G , Muluare PO , Gikunju S , Nderitu L , Balish A , Winchell J , Schneider E , Erdman D , Oberste MS , Katz MA , Breiman RF . PLoS One 2012 7 (8) e43656 BACKGROUND: Few comprehensive data exist on disease incidence for specific etiologies of acute respiratory illness (ARI) in older children and adults in Africa. METHODOLOGY/PRINCIPAL FINDINGS: From March 1, 2007, to February 28, 2010, among a surveillance population of 21,420 persons >5 years old in rural western Kenya, we collected blood for culture and malaria smears, nasopharyngeal and oropharyngeal swabs for quantitative real-time PCR for ten viruses and three atypical bacteria, and urine for pneumococcal antigen testing on outpatients and inpatients meeting a ARI case definition (cough or difficulty breathing or chest pain and temperature >38.0 degrees C or oxygen saturation <90% or hospitalization). We also collected swabs from asymptomatic controls, from which we calculated pathogen-attributable fractions, adjusting for age, season, and HIV-status, in logistic regression. We calculated incidence by pathogen, adjusting for health-seeking for ARI and pathogen-attributable fractions. Among 3,406 ARI patients >5 years old (adjusted annual incidence 12.0 per 100 person-years), influenza A virus was the most common virus (22% overall; 11% inpatients, 27% outpatients) and Streptococcus pneumoniae was the most common bacteria (16% overall; 23% inpatients, 14% outpatients), yielding annual incidences of 2.6 and 1.7 episodes per 100 person-years, respectively. Influenza A virus, influenza B virus, respiratory syncytial virus (RSV) and human metapneumovirus were more prevalent in swabs among cases (22%, 6%, 8% and 5%, respectively) than controls. Adenovirus, parainfluenza viruses, rhinovirus/enterovirus, parechovirus, and Mycoplasma pneumoniae were not more prevalent among cases than controls. Pneumococcus and non-typhi Salmonella were more prevalent among HIV-infected adults, but prevalence of viruses was similar among HIV-infected and HIV-negative individuals. ARI incidence was highest during peak malaria season. CONCLUSIONS/SIGNFICANCE: Vaccination against influenza and pneumococcus (by potential herd immunity from childhood vaccination or of HIV-infected adults) might prevent much of the substantial ARI incidence among persons >5 years old in similar rural African settings. |
Viral and bacterial causes of severe acute respiratory illness among children less than 5 years old in a high malaria prevalence area of western Kenya, 2007-2010
Feikin DR , Njenga MK , Bigogo G , Aura B , Aol G , Audi A , Jagero G , Muluare PO , Gikunju S , Nderitu L , Winchell JM , Schneider E , Erdman DD , Oberste MS , Katz MA , Breiman RF . Pediatr Infect Dis J 2012 32 (1) e14-9 BACKGROUND: Few comprehensive data exist on the etiology of severe acute respiratory illness (SARI) among African children. METHODS: From March 1, 2007, to February 28, 2010, we collected blood for culture and nasopharyngeal and oropharyngeal swabs for real-time quantitative PCR for ten viruses and three atypical bacteria among children <5 years old with SARI, defined as WHO-classified severe or very severe pneumonia or oxygen saturation <90%, who visited a clinic in rural western Kenya. We collected swabs from controls without febrile or respiratory symptoms. We calculated odds ratios (OR) for infection among cases, adjusting for age and season in logistic regression. We calculated SARI incidence, adjusting for healthcare-seeking for SARI in the community. RESULTS: 2,973 SARI cases were identified (54% inpatient, 46% outpatient), yielding an adjusted incidence of 56 cases per 100 person-years. A pathogen was detected in 3.3% of non-contaminated blood cultures; non-typhi Salmonella (1.9%) and Streptococcus pneumoniae (0.7%) predominated. A pathogen was detected in 84% of nasopharyngeal/oropharyngeal specimens, the most common being rhino/enterovirus (50%), respiratory syncytial virus (RSV, 22%), adenovirus (16%) and influenza viruses (8%). Only RSV and influenza viruses were found more commonly among cases than controls (OR 2.9, 95% CI 1.3-6.7 and OR 4.8, 95% CI 1.1-21, respectively). Incidence of RSV, influenza viruses and S. pneumoniae were 7.1, 5.8 and 0.04 cases per 100 person-years, respectively. CONCLUSIONS: Among Kenyan children with SARI, RSV and influenza virus are the most likely viral causes and pneumococcus the most likely bacterial cause. Contemporaneous controls are important for interpreting upper respiratory tract specimens. |
Sequential Rift Valley fever outbreaks in eastern Africa caused by multiple lineages of the virus
Nderitu L , Lee JS , Omolo J , Omulo S , O'Guinn ML , Hightower A , Mosha F , Mohamed M , Munyua P , Nganga Z , Hiett K , Seal B , Feikin DR , Breiman RF , Njenga MK . J Infect Dis 2011 203 (5) 655-65 BACKGROUND: During the Rift Valley fever (RVF) epidemic of 2006-2007 in eastern Africa, spatial mapping of the outbreaks across Kenya, Somalia, and Tanzania was performed and the RVF viruses were isolated and genetically characterized. METHODS: Following confirmation of the RVF epidemic in Kenya on 19 December 2006 and in Tanzania on 2 February 2007, teams were sent to the field for case finding. Human, livestock, and mosquito specimens were collected and viruses isolated. The World Health Organization response team in Kenya worked with the WHO's polio surveillance team inside Somalia to collect information and specimens from Somalia. RESULTS: Seven geographical foci that reported hundreds of livestock and >25 cases in humans between December 2006 and June 2007 were identified. The onset of RVF cases in each epidemic focus was preceded by heavy rainfall and flooding for at least 10 days. Full-length genome analysis of 16 RVF virus isolates recovered from humans, livestock, and mosquitoes in 5 of the 7 outbreak foci revealed 3 distinct lineages of the viruses within and across outbreak foci. CONCLUSION: The findings indicate that the sequential RVF epidemics in the region were caused by multiple lineages of the RVF virus, sometimes independently activated or introduced in distinct outbreak foci. |
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