Last data update: May 20, 2024. (Total: 46824 publications since 2009)
Records 1-7 (of 7 Records) |
Query Trace: Knobel D [original query] |
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Animal-related factors associated with moderate-to-severe diarrhea in children younger than five years in western Kenya: A matched case-control study
Conan A , O'Reilly CE , Ogola E , Ochieng JB , Blackstock AJ , Omore R , Ochieng L , Moke F , Parsons MB , Xiao L , Roellig D , Farag TH , Nataro JP , Kotloff KL , Levine MM , Mintz ED , Breiman RF , Cleaveland S , Knobel DL . PLoS Negl Trop Dis 2017 11 (8) e0005795 BACKGROUND: Diarrheal disease remains among the leading causes of global mortality in children younger than 5 years. Exposure to domestic animals may be a risk factor for diarrheal disease. The objectives of this study were to identify animal-related exposures associated with cases of moderate-to-severe diarrhea (MSD) in children in rural western Kenya, and to identify the major zoonotic enteric pathogens present in domestic animals residing in the homesteads of case and control children. METHODOLOGY/PRINCIPAL FINDINGS: We characterized animal-related exposures in a subset of case and control children (n = 73 pairs matched on age, sex and location) with reported animal presence at home enrolled in the Global Enteric Multicenter Study in western Kenya, and analysed these for an association with MSD. We identified potentially zoonotic enteric pathogens in pooled fecal specimens collected from domestic animals resident at children's homesteads. Variables that were associated with decreased risk of MSD were washing hands after animal contact (matched odds ratio [MOR] = 0.2; 95% CI 0.08-0.7), and presence of adult sheep that were not confined in a pen overnight (MOR = 0.1; 0.02-0.5). Variables that were associated with increased risk of MSD were increasing number of sheep owned (MOR = 1.2; 1.0-1.5), frequent observation of fresh rodent excreta (feces/urine) outside the house (MOR = 7.5; 1.5-37.2), and participation of the child in providing water to chickens (MOR = 3.8; 1.2-12.2). Of 691 pooled specimens collected from 2,174 domestic animals, 159 pools (23%) tested positive for one or more potentially zoonotic enteric pathogens (Campylobacter jejuni, C. coli, non-typhoidal Salmonella, diarrheagenic E. coli, Giardia, Cryptosporidium, or rotavirus). We did not find any association between the presence of particular pathogens in household animals, and MSD in children. CONCLUSIONS AND SIGNIFICANCE: Public health agencies should continue to promote frequent hand washing, including after animal contact, to reduce the risk of MSD. Future studies should address specific causal relations of MSD with sheep and chicken husbandry practices, and with the presence of rodents. |
Prevalence and diversity of small mammal-associated Bartonella species in rural and urban Kenya.
Halliday JE , Knobel DL , Agwanda B , Bai Y , Breiman RF , Cleaveland S , Njenga MK , Kosoy M . PLoS Negl Trop Dis 2015 9 (3) e0003608 Several rodent-associated Bartonella species are human pathogens but little is known about their epidemiology. We trapped rodents and shrews around human habitations at two sites in Kenya (rural Asembo and urban Kibera) to determine the prevalence of Bartonella infection. Bartonella were detected by culture in five of seven host species. In Kibera, 60% of Rattus rattus were positive, as compared to 13% in Asembo. Bartonella were also detected in C. olivieri (7%), Lemniscomys striatus (50%), Mastomys natalensis (43%) and R. norvegicus (50%). Partial sequencing of the citrate synthase (gltA) gene of isolates showed that Kibera strains were similar to reference isolates from Rattus trapped in Asia, America, and Europe, but that most strains from Asembo were less similar. Host species and trapping location were associated with differences in infection status but there was no evidence of associations between host age or sex and infection status. Acute febrile illness occurs at high incidence in both Asembo and Kibera but the etiology of many of these illnesses is unknown. Bartonella similar to known human pathogens were detected in small mammals at both sites and investigation of the ecological determinants of host infection status and of the public health significance of Bartonella infections at these locations is warranted. |
High prevalence of Rickettsia africae variants in Amblyomma variegatum ticks from domestic mammals in rural western Kenya: implications for human health
Maina AN , Jiang J , Omulo SA , Cutler SJ , Ade F , Ogola E , Feikin DR , Njenga MK , Cleaveland S , Mpoke S , Ng'ang'a Z , Breiman RF , Knobel DL , Richards AL . Vector Borne Zoonotic Dis 2014 14 (10) 693-702 Tick-borne spotted fever group (SFG) rickettsioses are emerging human diseases caused by obligate intracellular Gram-negative bacteria of the genus Rickettsia. Despite being important causes of systemic febrile illnesses in travelers returning from sub-Saharan Africa, little is known about the reservoir hosts of these pathogens. We conducted surveys for rickettsiae in domestic animals and ticks in a rural setting in western Kenya. Of the 100 serum specimens tested from each species of domestic ruminant 43% of goats, 23% of sheep, and 1% of cattle had immunoglobulin G (IgG) antibodies to the SFG rickettsiae. None of these sera were positive for IgG against typhus group rickettsiae. We detected Rickettsia africae-genotype DNA in 92.6% of adult Amblyomma variegatum ticks collected from domestic ruminants, but found no evidence of the pathogen in blood specimens from cattle, goats, or sheep. Sequencing of a subset of 21 rickettsia-positive ticks revealed R. africae variants in 95.2% (20/21) of ticks tested. Our findings show a high prevalence of R. africae variants in A. variegatum ticks in western Kenya, which may represent a low disease risk for humans. This may provide a possible explanation for the lack of African tick-bite fever cases among febrile patients in Kenya. |
Urban leptospirosis in Africa: a cross-sectional survey of leptospira infection in rodents in the Kibera urban settlement, Nairobi, Kenya
Halliday JE , Knobel DL , Allan KJ , de CBronsvoort BM , Handel I , Agwanda B , Cutler SJ , Olack B , Ahmed A , Hartskeerl RA , Njenga MK , Cleaveland S , Breiman RF . Am J Trop Med Hyg 2013 89 (6) 1095-102 Leptospirosis is a widespread but under-reported cause of morbidity and mortality. Global re-emergence of leptospirosis has been associated with the growth of informal urban settlements in which rodents are thought to be important reservoir hosts. Understanding the multi-host epidemiology of leptospirosis is essential to control and prevent disease. A cross-sectional survey of rodents in the Kibera settlement in Nairobi, Kenya was conducted in September-October 2008 to demonstrate the presence of pathogenic leptospires. A real-time quantitative polymerase chain reaction showed that 41 (18.3%) of 224 rodents carried pathogenic leptospires in their kidneys, and sequence data identified Leptospira interrogans and L. kirschneri in this population. Rodents of the genus Mus (37 of 185) were significantly more likely to be positive than those of the genus Rattus (4 of 39; odds ratio = 15.03). Questionnaire data showed frequent contact between humans and rodents in Kibera. This study emphasizes the need to quantify the public health impacts of this neglected disease at this and other urban sites in Africa. |
Global distribution of Bartonella infections in domestic bovine and characterization of Bartonella bovis strains using multi-locus sequence typing.
Bai Y , Malania L , Alvarez Castillo D , Moran D , Boonmar S , Chanlun A , Suksawat F , Maruyama S , Knobel D , Kosoy M . PLoS One 2013 8 (11) e80894 Bartonella bovis is commonly detected in cattle. One B. bovis strain was recently isolated from a cow with endocarditis in the USA, suggesting its role as an animal pathogen. In the present study, we investigated bartonella infections in 893 cattle from five countries (Kenya, Thailand, Japan, Georgia, and Guatemala) and 103 water buffaloes from Thailand to compare the prevalence of the infection among different regions and different bovid hosts. We developed a multi-locus sequence typing (MLST) scheme based on nine loci (16S rRNA, gltA, ftsZ, groEL, nuoG, ribC, rpoB, ssrA, and ITS) to compare genetic divergence of B. bovis strains, including 26 representatives from the present study and two previously described reference strains (one from French cows and another from a cow with endocarditis in the USA). Bartonella bacteria were cultured in 6.8% (7/103) of water buffaloes from Thailand; all were B. bovis. The prevalence of bartonella infections in cattle varied tremendously across the investigated regions. In Japan, Kenya, and the Mestia district of Georgia, cattle were free from the infection; in Thailand, Guatemala, and the Dusheti and Marneuli districts of Georgia, cattle were infected with prevalences of 10-90%. The Bartonella isolates from cattle belonged to three species: B. bovis (n=165), B. chomelii (n=9), and B. schoenbuchensis (n=1), with the latter two species found in Georgia only. MLST analysis suggested genetic variations among the 28 analyzed B. bovis strains, which fall into 3 lineages (I, II, and III). Lineages I and II were found in cattle while lineage III was restricted to water buffaloes. The majority of strains (17/28), together with the strain causing endocarditis in a cow in the USA, belonged to lineage I. Further investigations are needed to determine whether B. bovis causes disease in bovids. |
Coxiella burnetii in humans, domestic ruminants, and ticks in rural western Kenya
Knobel DL , Maina AN , Cutler SJ , Ogola E , Feikin DR , Junghae M , Halliday JE , Richards AL , Breiman RF , Cleaveland S , Njenga MK . Am J Trop Med Hyg 2013 88 (3) 513-518 We conducted serological surveys for Coxiella burnetii in archived sera from patients that visited a rural clinic in western Kenya from 2007 to 2008 and in cattle, sheep, and goats from the same area in 2009. We also conducted serological and polymerase chain reaction-based surveillance for the pathogen in 2009-2010, in human patients with acute lower respiratory illness, in ruminants following parturition, and in ticks collected from ruminants and domestic dogs. The IgG antibodies against C. burnetii were detected in 30.9% (N = 246) of archived patient sera and in 28.3% (N = 463) of cattle, 32.0% (N = 378) of goats, and 18.2% (N = 159) of sheep surveyed. Four of 135 (3%) patients with acute lower respiratory illness showed seroconversion to C. burnetii. The pathogen was detected by polymerase chain reaction in specimens collected from three of six small ruminants that gave birth within the preceding 24 hours, and in five of 10 pools (50%) of Haemaphysalis leachi ticks collected from domestic dogs. |
Rickettsia felis infection in febrile patients, western Kenya, 2007-2010
Maina AN , Knobel DL , Jiang J , Halliday J , Feikin DR , Cleaveland S , Ng'ang'a Z , Junghae M , Breiman RF , Richards AL , Njenga MK . Emerg Infect Dis 2012 18 (2) 328-31 To determine previous exposure and incidence of rickettsial infections in western Kenya during 2007-2010, we conducted hospital-based surveillance. Antibodies against rickettsiae were detected in 57.4% of previously collected serum samples. In a 2008-2010 prospective study, Rickettsia felis DNA was 2.2x more likely to be detected in febrile than in afebrile persons. |
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