ABSTRACT
Introduction: Rotavirus A (RVA) is a
leading cause of acute infant gastroenteritis in Mozambique, responsible for
approximately 13,000 annual infant deaths in peri-urban and other areas.
Aim: the present review aimed
summarize the most relevant and recent literature regarding RVA infection in
Mozambique.
Methods: the documents were
obtained from electronic databases such as PubMed, Google Scholar, Scinapse,
Scilit, and Microsoft Academic to find the leading scientific publications
related to Mozambique's RVA.
Findings: The search allowed us to
find 20 peer-reviewed journal articles, three official reports, eight abstracts
from national conferences, one thesis, and other documents to supplement the
information. Rotavirus frequency ranged between 24 to 42.4%, 34.8% attributable
to Mozambique. Most data are hospital-based from Maputo, Sofala, Zambézia, and
Nampula provinces. Nampula province shows the highest number of cases. Thus,
there might be some bias on the geographical distribution of the virus. The
prevalence is high in children less than one year. Regarding the control, the
Expanded Program on Immunization (EPI) introduced a monovalent vaccine in
September 2015 (Rotarix), which positively impacted the reduction of RVA cases.
After vaccine introduction, a high diversity of RVA genotypes was observed, with
the predominance of G1P[8] and the emergence of G9P[4], G9P[6], G3P[4].
However, only the whole genome sequence can confirm if it is due to the natural
genotypes fluctuation. RVA infection was detected in swine, and a recent
analysis reported an RVA strain from children clustered with different animal
strains.
Conclusion: The scarce yet highly
reliable research resources allowed scientists to detect RVA G1P[8] and other
genotypes, potential animal reservoirs, and to find that RVA is more prevalent
during the transition dry-rainy season, and the virus becomes more frequent
when children approach the 11th month, to then decline as they age.
It is essential to develop studies providing a broad view of RVA reservoirs as
part of the strategy to control its dissemination.
Keywords: Rotavirus infections;
Children; Diarrhea; Mozambique
INTRODUCTION
Diarrhea remains a tremendous public health problem
globally and is associated with 446,000 deaths among children under five years
old in 2016 1.
In Mozambique, even with the strategies implemented to reduce diarrhea cases in
the last two decades (improving hygiene, sanitation, and access to clean water)
2,
diarrhea remains the leading cause of mortality of children under five years
old, with 4383 deaths annually 1.
Rotavirus, particularly group A (RVA) 3,
is among the significant causes of acute infant gastroenteritis globally 1,4. Data from the global burden of annual RVA mortality shows that in 2016,
about 128,500 children under five years old died, of which 104,733 in
sub-Saharan Africa 1.
The World
Health Organization 5 (WHO) recommended introducing the rotavirus
vaccine in countries with high prevalence and countrywide continuous
surveillance before and after the vaccine's introduction.
The
global enteric multicenter study (GEMS) showed RVA as the leading cause of
diarrheic diseases in Mozambique with an attributable factor of 34.8% and
reported a prevalence ranging from 24 - 42.4% 6.
Nevertheless, there is very little published literature on Mozambique's RVA and
its impact on human or animal health, particularly in the northern and central
regions of the country 2,7-10. Thus, there is a need to expand surveillance
and epidemiological studies to understand the impact of local strains and
improve the current control measures 9-11. It is also essential to
identify the strains and compare them with others from different countries to
understand the molecular epidemiology and design appropriate measures. Thus,
this study reviews the most relevant information on RVA infection in Mozambique.
METHODS
We used Google Scholar, Scinapse, Scilit,
PubMed, Scielo, and Microsoft Academic to find the leading scientific
publications related to Mozambique's RVA to write this manuscript. The leading
search keywords were "rotavirus" and "Mozambique." We selected
scholarly documents with keywords or related in the title. In some cases, the
titles presented Mozambique's districts or provinces' names, and some of the
documents were about Rotavirus and other diarrheic diseases.
We found 20 peer-reviewed journal articles,
three official reports, eight abstracts from national conferences, and one
thesis through the search. We added other elements such as the map and figure
as we reviewed the primary sources.
We analyzed the documents using the
qualitative data analysis software Atlas.ti 9 (Atlas.ti Scientific Software
Development GmbH, Berlin, 2020), using the codes "etiology,"
"transmission," "geographical distribution,"
"susceptible groups," "vaccination," "impact,
surveillance, treatment," and "infrastructure." Then, we
summarized the data into a coherent text, using other sources from the
literature to provide more consistency to the text.
RESULTS AND DISCUSSION
Geographical distribution
First, it is essential to make a brief
description of Mozambique (Map 1) so that anyone can easily understand how
spread RVA is in Mozambique according to the current scholarly information. It
is a tropical country with 801,590 km2, located in Southeastern
Africa, divided into eleven provinces, with an eastern coastline (Indian Ocean)
from north to south. According to the last census (2017) 12, the population comprises
27,909,798 inhabitants, significantly below poverty. Diarrheic diseases are
common and reported as the fourth major cause of mortality in children aged
five years or less 2.
Map 1 - Mozambique, the country's regions, and
cities. United Nations 16, under public domain
Rotavirus is highly prevalent among <
5-year old children in Mozambique 13. Thus, non-surprisingly, there
have been reports from different country areas. de Deus et al. 14 mentioned six
surveillance sites from the National Surveillance of Diarrhea (ViNaDia):
Hospital Geral José Macamo, Hospital Geral de Mavalane and Hospital Central de
Maputo(Maputo City), Hospital Geral de Quelimane (Zambézia Province), Hospital
Central da Beira (Sofala Province), and Hospital Central de Nampula (Nampula
Province). ViNaDia surveillance system produces most of the data on the
epidemiology of RVA in Mozambique. INS is the leading institution studying RVA
in Mozambique 10. For the sake of research, the
reference mentioned above virology laboratory of INS has the country's
state-of-the-art equipment for RVA analysis 7,15, an integral component to
achieve ViNaDia's goals. Manhiça Health Research Center (CISM) also develops
studies on RVA10. Another laboratory with
comparable equipment in the Directorate for Animal Sciences of the National
Institute for Agricultural Research (IIAM) 8,9.
Nampula has registered the highest number of cases (see
details in subsection 5.3) 7. There are potential
explanations for why this province presented most cases. For instance, (1)
Nampula is the most populated province 12, and (2) there are serious
hygiene issues in Nampula's urban areas impacting the spread of diarrheic
diseases 17. A recent analysis of the
epidemiology of Rotavirus in Nampula observed that piped water was associated
with rotavirus infection and suggested that this can be related to the water
network that is old and damaged, while in the post-vaccine period age, year,
and contact with different animals were associated with rotavirus infection 18. It would be worthy of
studying the epidemiology of RVA in the Novo Bairro area of Quelimane city,
well-known as an urban area with very precarious sanitation and a history of
cholera outbreak 30.
Mussa et al. 19 reported cases in
the cities of Maputo and Matola, RVA infection was reported by de Deus et al. 14, in children
less than five years old with diarrhea in Mavalane General Hospital (Maputo
City) in 41.3% and Manhiça District Hospital (Maputo Province) in 44.3% 14. On the other hand, Langa et al. 11 reported RVA
infections in Chókwè District (Gaza Province) in 24.0% 11. Based on the ViNaDiA
platform, RVA infection was reported in four provinces of the country: Maputo
city (southern region of the country), Sofala, Zambézia (Center region of the country),
and Nampula (Northern region of the country), ranging from 12.2% - 40.2%
regardless to the vaccine introduction period 14,20.
Vaccination
So far, there are four licensed vaccines for Rotavirus in
the world: the pentavalent RotaTeq™, monovalent Rotatrix™ (GlaxoSmithKline
Biologicals, Rixansart, Belgium), Rotavac® (Bharat Biotech, India), and
Rotasiil® (Serum Institute of India Pvt. Ltd. India) 21. Mozambique introduced
Rotatrix™ in September 2015 as part of the National Immunization Program. The
Instituto Nacional de Saúde and partner organizations have been assessing the
vaccination outcomes. After vaccine introduction, there was a significant
reduction in diarrhea hospitalization and rotavirus infection, from 40.2% in
2014 to 13.5% in 2017, and reduction cases occurred in undernourished children
from 42.7% to 12.2% 18.
Susceptible
groups
RVA is
frequent in children up to 5 years old, with a slight majority in male
patients 18,22. A study reported the
median age of hospitalization of 9 months in 2014 and 11 in 2015 during the
pre-vaccine period than ten months in 2016 and 2017 in the post-vaccine period.
In Chókwè, Langa et al. 11 found 94.1% of
children positive for Rotavirus aged up to two years old. de Deus et al. 22 in Manhiça and
Mavalane found 52.7% of RVA cases in children from 0 to 11 months. Similar
results were found in a case-control study conducted in Manhiça, where children
under one year had an attributable fraction of 34.8% of RVA infection 23. Thus, these findings suggest
that RVA infection is higher in children less than one year and decreases as
they grow up.
Molecular
characterization of RVA
Mozambique uses the WHO’s algorithm for RVA detection and
characterization 24. Several studies on RVA uses
ELISA through the commercial kits, mainly Prospect Oxoid with a specificity of
99.2% (96% - 100%) and sensitivity of 100% (95% - 100%). Reverse-transcriptase
polymerase chain reaction (RT-PCR) performs the molecular characterization of
RVA based on two significant proteins, VP7 and VP4, which gives the genotype
combination G and P. The complete genome sequence is essential to perform the
phylogenetic analysis and sequences comparison.
Globally the most common RVA genotypes are G1P[8], G2P[4],
G3P[8], and G4P[8], being G1P[8] the most prevalent 25,26. Studies conducted before
the introduction of the vaccine in Mozambique (2015) reported G12P[8], G1P[8],
and G12P[6] as the most common genotypes in Chokwé, a rural area in the
Southern region of Mozambique 27. João et al. 28, in a study
conducted in rural (Manhiça) and urban (Maputo city) areas, found G2P[4] and
G12P[6] as the most prevalent genotypes. However, after
vaccine introduction, a high diversity of RVA genotypes was observed, including
the emergency of G9P[4], G9P[6], G3P[4], and G3P[8] in Mozambique 29. Other authors also analyzed
the most frequent genotypes in children with diarrhea but different areas 11. The vaccine seems to
contribute to the increased diversity and uncommon strains
circulating as G3P[4] and G3P[8], G4P[6]. However, only the complete genome
sequences can confirm if it is due to the fluctuation of natural genotypes or
the pressure of the vaccine.
RVA
transmission pathways
RVA is a
zoonotic virus able to be transmitted between different species. Swine is a
significant reservoir 30, and P[6] strain has been
reported in animals and children with diarrhea 11. In Chòkwé, this strain was
detected in children and clustered with three porcine prototype strains 11. This finding shows the
possible zoonotic RV transmission in Mozambique. There is a long way to build a
concise body of knowledge on RVA in animals in Mozambique, but the currently
known studies are a good starting point.
Figure 1 - Rotavirus transmission pathway. The vertical blue
lines represent barriers to transmission. Adapted from the following sources:
UNICEF Philippines et al. 34, licensed under the Creative Commons Attribution
(CC-BY) 2.0 Generic; Beards 35, under CC-BY 3.0 Unported; Henderson 36, under
Creative Commons 1.0 Universal Public Domain Dedication (CC0); and 37, licensed
under Pixabay License (free for commercial use, no attribution required).
The reported data of Rotavirus in animals suggest the
implantation of surveillance of Rotavirus in animals 31. However, additional studies
are needed to understand better the role of animals in the transmission of RVA
in the country and the emergency of new strains.
RVA is a public health concern due to poor hygiene and
environmental contamination (Fig. 1) 8. Whole-genome sequencing of a
mixed stool containing G12 and GXP[14] strains showed that the last one
clustered with sequences from a diverse group of animal strains, highlighting
the possible interspecies transmission of RVA in the country 32. It was also observed that
swine could carry the RVA without symptoms 9. However, it is necessary to
deepen the current knowledge on RVA reservoirs in Mozambique.
Most of the studies that analyzed the monthly distribution
of RVA cases showed that the highest prevalence occurs during the cold/dry
season 11,14,18. The authors reported
that RVA is more frequent during July, August, and September, with relatively
low temperatures and low rainfall 11,14,18. Furthermore, D'Souza et al. 33 performed a
similar study in three Australian cities (Brisbane, Melbourne, and Canberra) and
found similar results, suggesting that this trend is worldwide. However, since
the vaccine was introduced, cases were shifted to the wet season (October and
November) in Nampula province Northern of Mozambique 18. It would be helpful to study
how exactly weather affects the prevalence of RVA.
Health and
commercial impact
In Mozambique, RVA is a significant cause of acute
gastroenteritis and is associated with symptoms such as diarrhea 13,15, vomiting 38, resulting in dehydration 39, and
undernutrition 22. RVA and other diarrheic
diseases often demand high costs of medical assistance and hospitalization 7,15. Swine presents similar
symptoms as humans, varying in severity, resulting in significant losses in the
commercial and familiar sectors 31.
CONCLUSION
Mozambique has data on RVA from surveillance and studies.
Methods such as ELISA and RT-PCR provide highly reliable results, but they
might be costly for routine analyzes. It would be valuable to promote more
basic epidemiological and social research on RVA and build a more robust body
of knowledge.
RVA affects Mozambique's infant health, particularly in
children less than one-year-old. The prevalence has declined since the
introduction of the vaccine.
The predominant genotypes change over time, and the most
recent data point to the G1P[8] as the most common. The current epidemiological
information might not reflect the country's current situation because most data
came from Maputo City and province, Sofala, Zambézia, and Nampula provinces.
There shall also be surveys in the community, rather than data only from people
seeking medical care.
RVA also occurs in swine in Mozambique, but the virus is
likely to occur in other carriers. It is essential to develop studies providing
a broad view of RVA reservoirs as part of the strategy to control its
dissemination.
Data
confidentiality
The authors declare having
followed the protocols in use at their working center regarding patients’ data
publication.
Competing interests
The authors declare that there
are no conflits of interest nor any form of support.
Funding sources
This research received no
speci¿c grant from any funding agency in the public, commercial, or
not-for-pro¿t sectors.
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