Causes of diarrhea among children under five years of age in Tanzania
Mapping of diarrheal disease microbial pathogens, such as viruses, bacteria and intestinal parasites, in children under 5 years of age in order to gather knowledge and raise awareness about the need for control strategies involving collaborative efforts from veterinary and human medicine.
About the research project
Diarrhea kills 2 million people each year, majority of which are children under the age of two. Pathogens causing diarrheal disease can be roughly sorted into three categories:
- viruses (i.e. rotaviruses, noroviruses genogroup II)
- bacteria (i.e. Campylobacter and Enterobacteriaceae, such as Shigella and Escherichia coli)
- intestinal parasites (i.e. Cryptosporidium parvum/hominis, Entamoeba histolytica, Giardia lamblia).
Aim of this study is to determine the magnitude, co-morbidity pattern and risk factors of gastrointestinal infections among children under the age of five.
The study included patients who were presenting with diarrhea compared to those without diarrhea, and stool samples were collected.
Each diarrheal pathogen is capable of causing disease alone, but diarrhea also occurs in the presence of two or more pathogens, called coinfections. We published that coinfections are frequent in our patient cohort, and that the pathogenicity of each organism appears to be enhanced by some coinfections and weakened by others. Interestingly, severity of diarrhea did not correlate with coinfections. (2)
Viral pathogens
More than a third of diarrhea hospitalizations among children under five years of age is attributed to rotavirus infection in Tanzania. Two oral vaccines have been developed but they target limited number of viral strains. This study showed that viral strain G1 is the predominant strain in Tanzania. However, the same strain is not targeted by the approved vaccines. (7)
In the same patient cohort, we found children affected by diarrhea had more often been infected with noroviruses than the healthy controls. Additionally the noroviral genetic diversity in diarrheal cases was higher. Finally, norovirus infection was more common in children below first year of age. (6)
Our analysis of human adenoviruses (HAdV) suggested that HAdV is not an important cause of diarrhea in young HIV-positive children, although it causes stomach flu in children of all tested ages, and systematic infection in children under one year of age. (5)
Bacterial pathogens
Presence of antibiotic-resistant bacteria in the gastrointestinal tract (faecal carriage) is a potential risk for transmission and infection. We report in this study a high rate of faecal carriage of antibiotic-resistant, ESBL-producing Enterobacteriaceae among children below two years of age in Tanzania, particularly those with HIV-infection. Resistance to the majority of the available antimicrobials commonly used for children in Tanzania leaves few treatment options for infections caused by these pathogens. (3)
In this study we also investigated if horisontal plasmid transfer, a mechanism of spreading antimicrobial resistance, is present in the pediatric cohort. Analysis of Klebsiella pneumoniae isolates from stool samples of both healthy and children with diarrhea revealed an epidemic spread of a resistance plasmid, and that it was the key factor for dissemination of extended spectrum betalactamases which render antibiotic resistance. (1)
Parasitic pathogens
Analysis of parasites showed that Cryptosporidium infection is common among young Tanzanian children with diarrhea, particularly those living with HIV, and infection is more frequent during the rainy season. Giardia lamblia is frequently implicated in asymptomatic infections, but rarely causes overt diarrheal illness, and its prevalence increases with age.
Collaborating institutions
This study is a close collaboration with and Muhimbili University of Health and Allied Sciences (), Dar es Salaam, Tanzania.
Publications
Relevant publications
- (2020)
- (2017)
- (2016)
- (2015)
- (2014)
- (2014)
- . (2014)
People
Project manager
Project members
Marit G. Tellevik National Centre for Tropical Infectious Diseases, Department of Medicine, Haukeland University Hospital, Bergen, Norway.
Samuel Y. Maselle Department of Microbiology and Immunology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
Torunn Hjøllo Department of Clinical Science, University of Bergen, Bergen, Norway
Øyvind Kommedal Department of Microbiology, Haukeland University Hospital, Bergen, Norway
Kirsti Vainio Division of Infectious Disease Control, Norwegian Institute of Public Health, Oslo, Norway
Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, Norway
Torunn Pedersen Department of Microbiology and Infection Control, University Hospital of North Norway, Tromsø, Norway
Paul Christoffer Lindemann Department of Microbiology, Haukeland University Hospital, Bergen, Norway
Jessin Janice Department of Microbiology, Oslo University Hospital, Norway
Department of Pharmacy, UiT-The Arctic University of Norway, Tromsø, Norway