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KSR Number: KSRA129466

Emerging and re-emerging human infectious diseases: a systematic review of the role of wild animals with a focus on public health impact

  • Asian Pac J Trop Med 2020;13(3);99-106

Risk of Bias Assessment

Overall summary: High risk of bias in the review

Bottom Line

There is some evidence, from a wide range of geographic regions, to suggest that wild animals (mainly bats, birds and primates) may play a role in the dissemination of aetiological agents (mainly viruses). The review authors concluded that the monitoring of these diseases and adequate preparation for possible epidemics and pandemics are fundamental conditions for the mitigation of their future impact. Weaknesses in the search process mean that relevant studies may have been missed and the description of the included studies and their findings was limited.

Risk of Bias Assessment

Overall summary High risk of bias in the review

High

Weaknesses in the search process mean that relevant studies may have been missed and the description of the included studies and their findings was limited.

A. Did the interpretation of findings address all of the concerns identified in Domains 1 to 4? No
B. Was the relevance of identified studies to the review's research question appropriately considered? Probably yes
C. Did the reviewers avoid emphasizing results on the basis of their statistical significance? Probably yes
Risk of bias in the review High

Details of Review

Number of studies 19
Number of participants NA
Last search date April 2019
Review type Aetiological
Objective To review studies on the role of wild animals as reservoirs and/or dispersers of etiological agents of human infectious diseases in order to compile data on the main wild animals and etiological agents involved in zoonotic outbreaks
Population Unclear
Outcome Human infectious diseases which might have the participation of wild animals in their transmission cycle.
Study design Unclear
Exposure Wild animals (including bats, wild birds, amphibians, non-human primates, pigs and wild boars, wild rodents, dromedaries, African buffalo, monkeys, wild and domestic dogs) participating in the transmission or dispersion of aetiological agents of human diseases.

Results

The included studies were conducted worldwide (n=8), in the African continent (n=2) or South Africa (n=1), in Columbia (n=3), in Brazil (n=3), in Italy (n=1) and in Malaysia (n=1).

The majority of zoonoses reported in the included studies (n=16) were linked to mammals, more expressively, with bats and non-human primates.The second largest group of animals identified as reservoirs or dispersers of aetiological agents of human infectious diseases were wild birds (n=7). There was one report of disease related to arthropods (ticks) and another to amphibians (salamanders).

The main aetiological agents reported were viral (n=16), with the minority being bacteria (n=2) and parasites (n=1). The aetiological agents identified included: Influenza Virus, Coronavirus, Nipah Virus, Ebola Virus, Paramyxovirus, Rhabdovirus, Hendra Virus, Menangle Virus, West Nile Virus, Bird Influenza, Filovirus, Human Immunodeficiency Virus (HIV), Orthohantavirus/Hantavirus, Human Type-4 Cells Lymphotropic Virus, Hepatitis E Virus, Leptospirosis, Borrelia burgdorferi, Marburg Virus, Rift Valley Fever Virus, Parvovirus, Arbovirus, and gastrointestinal parasites in general.

With respect to aetiological agents that can be transmitted directly to humans, without the need for wild animal reservoirs, wild animals function as reservoirs and dispersers. As the
wild animals remain asymptomatic, the aetiological agents can remain for long periods in nature, being dispersed expansively across geographical regions, and facilitating re-emergence of disease outbreaks (4 studies).

The review authors also stated that the perpetuation of viruses in accidental hosts is another factor promoting the emergence of new infectious diseases. The maintenance of viruses inside the body of an unusual host may increase the possibility of error in the process of RNA duplication and emergence of mutation in a relative short period. No references were provided for these statements.

Full Risk of Bias Assessment

The objective of the review was clearly stated and appropriate inclusion criteria were defined. No date or language restrictions were applied. Studies for which a complete text was not available were excluded.

1.1 Did the review adhere to pre-defined objectives and eligibility criteria? Probably yes
1.2 Were the eligibility criteria appropriate for the review question? Probably yes
1.3 Were eligibility criteria unambiguous? Probably yes
1.4 Were all restrictions in eligibility criteria based on study characteristics appropriate (e.g. date, sample size, study quality, outcomes measured)? Probably yes
1.5 Were any restrictions in eligibility criteria based on sources of information appropriate (e.g. publication status or format, language, availability of data)? Yes
Concerns regarding specification of study eligibility criteria Low

PubMed, Scopus and SciELO were searched for relevant studies. A simple search strategy was described and the search yield appeared low (n=245 records). No date or language restrictions were applied. The reference lists of selected articles were screened to identify further studies. The process of selecting studies for inclusion was unclear; the article states that " Having then obtained an ample amount of data from these filters, there was a consensus reached as to which articles would meet the inclusion criteria."

2.1 Did the search include an appropriate range of databases/electronic sources for published and unpublished reports? Probably no
2.2 Were methods additional to database searching used to identify relevant reports? Probably yes
2.3 Were the terms and structure of the search strategy likely to retrieve as many eligible studies as possible? Probably no
2.4 Were restrictions based on date, publication format, or language appropriate? Probably yes
2.5 Were efforts made to minimise error in selection of studies? No information
Concerns regarding methods used to identify and/or select studies High

Only very limited details of the included studies were provided, e.g. no detail of study design or of the human populations in which the infectious disease were identified. No information was provided about the data extraction process or the number of reviewers. No assessment of the methodological quality of included studies was reported.

3.1 Were efforts made to minimise error in data collection? No information
3.2 Were sufficient study characteristics considered for both review authors and readers to be able to interpret the results? Probably no
3.3 Were all relevant study results collected for use in the synthesis? Probably yes
3.4 Was risk of bias (or methodological quality) formally assessed using appropriate criteria? Probably no
3.5 Were efforts made to minimise error in risk of bias assessment? Probably no
Concerns regarding methods used to collect data and appraise studies High

The use of a narrative synthesis was appropriate. However, the description of the included studies was minimal and only qualitative results were provided.

4.1 Did the synthesis include all studies that it should? Probably yes
4.2 Were all pre-defined analyses reported or departures explained? Probably yes
4.3 Was the synthesis appropriate given the degree of similarity in the research questions, study designs and outcomes across included studies? Probably yes
4.4 Was between-study variation minimal or addressed in the synthesis? No information
4.5 Were the findings robust, e.g. as demonstrated through funnel plot or sensitivity analyses? Probably yes
4.6 Were biases in primary studies minimal or addressed in the synthesis? No information
Concerns regarding synthesis and findings Unclear

Abstract

Infectious diseases continue to impose unpredictable burdens on global health and economies, a subject that requires constant research and updates. In this sense, the objective of the present article was to review studies on the role of wild animals as reservoirs and/or dispersers of etiological agents of human infectious diseases in order to compile data on the main wild animals and etiological agents involved in zoonotic outbreaks. A systematic review was carried out using PRISMA guidelines, using the PubMed, Scopus and SciELO platforms as data banks. The descriptors used were 'zoonosis', 'human infectious diseases' and 'wild animals'. The results show that wild animals (mainly bats, birds and primates) play an important role in the dissemination of etiological agents (mainly viruses, as a new coronavirus called 2019 Novel Coronavirus) in extensive geographic regions. Moreover, these wild animal organisms can act as the site for essential biotic synergy among several pathogenic microorganisms, promoting a higher rate of adaptation, mutation and even genetic recombination, with consequent stimulation of new strains and subtypes, inducing new infectious agents with unknown virulent potential. In conclusion, the monitoring of these diseases and adequate preparation for possible epidemics and pandemics are fundamental conditions for the mitigation of their future impact. The zoonotic threat of these etiological agents and the impact on public health can be enormous as shown by the ongoing epidemic of 2019 novel coronavirus (2019- nCoV) infections.Copyright © 2020 Asian Pacific Journal of Tropical Medicine Produced by Wolters KluwerMedknow. All rights reserved.