Proposal for the control and prevention of Eastern Equine Encephalitis for
equines and humans in Ecuador.
Propuesta de control y prevención de Encefalitis Equina del Este para equinos y humanos del
Ecuador
Roberto Darwin Coello-Peralta.
Magister en Microbiología-mención Biomédica, Docente-Investigador de la Universidad de
Guayaquil, Guayaquil, Ecuador, roberto.coellope@ug.edu.ec, https://orcid.org/0000-0001-
5152-2843
María de Lourdes Salazar Mazamba.
PhD in Animal Science, Professor-Researcher at the University of Guayaquil, Guayaquil,
Ecuador, maría.salazarma@ug.edu.ec, https://orcid.org/0000-0002-3402-8058
Karla Lisseth Benítez Tierra.
Veterinarian-Zootechnician, University of Guayaquil, Guayaquil, Ecuador,
karla.benitezt@ug.edu.ec, https://orcid.org/0000-0001-5870-4957
Enrique Xavier Rodríguez Burnham.
Magister en Microbiología-mención Biomédica, Docente-Investigador de la Universidad de
Guayaquil, Guayaquil, Ecuador, xavier.rodriguezb@ug.edu.ec, https://orcid.org/0000-0002-
4275-3831
Valdez-Rivera Danilo
Master, Universidad Agraria del Ecuador, Faculty of Agricultural Sciences, Guayaquil,
Ecuador.
dvaldez@uagraria.edu.ec, https://orcid.org/0000-0002-5004-930X
Abstract
The objective of this research was: To make a proposal for the control and prevention of Eastern
Equine Encephalitis (EEE) for equines and humans in Ecuador, a search was applied in four
electronic databases in search of publications on the proposed topic that met the inclusion
criteria for the systematic review. Subsets of publications were subjected to a meta-analysis to
determine the best information on the topic. A total of 172 references published between 1938
and 2021 were included. EEE was reported throughout the Americas, from Canada to
Argentina with publications on natural infections since 1933, where it was first isolated in the
U.S., is now endemic in North America, and reaches South American ecosystems via infected
migratory birds. EEE is a notifiable disease, and causes fatal meningoencephalitis in equines
and humans; therefore, successful control of this arbovirosis is important.
roberto.coellope@ug.edu.ec
http://centrosuragraria.com/index.php/revista, Published by: Edwards Deming Institute,
Quito - Ecuador, April, June vol. 1. Num. 13 2022, This work is licensed under a Creative
Commons License, Attribution-NonCommercial-ShareAlike 4.0 International.
https://creativecommons.org/licenses/by-nc-sa/4.0/deed.es
92
Key words: VEEE, EEE. control and prevention, epidemiology, epidemiology
Resumen
La presente investigación tuvo como objetivo: Realizar una propuesta de control y prevención
de Encefalitis Equina del Este (EEE) para equinos y humanos del Ecuador, se aplicó una
búsqueda en cuatro bases de datos electrónicas en busca de publicaciones sobre la temática
propuestas que cumplieran con los criterios de inclusión para la revisión sistemática. Se
sometieron subconjuntos de publicaciones a un metaanálisis para determinar la mejor
información sobre el tema. Se incluyeron un total de 172 referencias publicadas entre 1938 y
2021. Se notificó EEE en todo el continente americano, desde Canadá hasta Argentina con
publicaciones sobre infecciones naturales desde 1933, donde se aisló por primera vez en los
EEUU., ahora es endémica en Norteamérica, y llega a ecosistemas sudamericanos a través de
las aves migratorias infectadas. La EEE es una enfermedad de declaración obligatoria, y causa
meningoencefalitis fatal en equinos y humanos; por lo consiguiente, es importante un control
exitoso de esta arbovirosis.
Palabras clave: Marketing, production, cocoa, export, positioning.
Introduction
The Eastern Equine Encephalitis Virus (EEEV) causes Eastern Equine Encephalitis (EEE)
which is characterized by causing febrile disease accompanied by fatal encephalitis in equines
and humans, with mortality percentages that can reach in humans between 30 to 70% (OIE,
2017, p. 16 ) and in equines between 70 to 90% (CFSPH, 2010, p.11Bingham et al., 2014;
CFSPH, 2017, p. 12), therefore, it is considered the most deadly arbovirus (virus transmitted
by arthropod vectors), in addition, it has an incubation period between 5 to 14 days (OIE, 2017,
p. 16).
The VEEE belonging to the Togaviridae family, Alphavirus species, generally has an enzootic
cycle and usually appears in Latin American ecosystems when infected migratory birds
(amplifying hosts) arrive to the wetlands and transmit the virus to native birds, preferably
through mosquitoes of the genus Culex, however, the infected vector bites domestic and wild
animals, being the susceptible hosts to the disease, equines and humans (PAHO/WHO, 2017).
Transmission of EEEV involves several birds of the order Passeriformes and Columbiformes
(Molaei et al., 2013), 26 species of mosquitoes, lice and chicken mites (CFSPH, 2017, p. 12),
amphibians, reptiles (Bingham et al., 2014) and mammals such as wild rodents, marsupials,
opossums (Mesa et al., 2005), bats (Blohm et al., 2018; Benvenuto et al., 2019), monkeys,
dogs, goats and small mammals; also, occasional cases of encephalitis have been reported in
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April - June vol. 1. Num. 13 2022
sheep, cattle, deer, South American camelids (llamas and alpacas) and pigs. (Go et al., 2014).
Thus, EEEV can establish a transmission network between several bird species, several
reservoirs, several vectors and susceptible hosts (Coello et al., 2020).
The virus was isolated for the first time, in 1933 in horses in New Jersey in the United States
(USA) (Feemster, 1938, p. 8; Fulton, 1940, p. 7), in 1955 in this country it was isolated in
mosquitoes, rodents and humans and in 1960 in birds according to Casals (1964, p. 19) and
Armstrong and Andreadis (2013, p. 4), then in 1982 it was isolated in dogs (Weaver et al.,
1994).
EEE in humans presents with fever, headache, irritability, stiff neck, confusion, drowsiness or
stupor, focal neurological impairment, disorientation, tremors, convulsions and paralysis,
although some patients go into coma, also, palpebral edema, abdominal pain, vomiting and
diarrhea may be observed (CFSPH, 2010, p. 11). In animals the disease presents with: High
fever, malaise, malaise, dullness, depression, lack of appetite, aimless walking, often in circles,
head pressure at corners, blindness, staggered and uncoordinated gait, reclining, convulsions
and death (in over 80% of cases) (Mackay, 2017, p. 91).
The Eastern Equine Encephalitis Virus is prevalent in the Americas from Canada to Argentina,
distinguishing 5 viral subtypes with high virulence and genetic variability (Mesa et al., 2005).
Between January 1 and October 20, 2020, the CDC reported 9 confirmed cases of EEE in the
USA, with cases in Indiana (1), Massachusetts (4), Michigan (2) and Wisconsin (2). (CDC,
2021). The purpose of the present work is to carry out a Proposal for the control and prevention
of Eastern Equine Encephalitis for equines and humans of Ecuador .
Materials and methods
The systematic review (SR) and meta-analysis (MA) were conducted according to inclusion
and exclusion criteria that were defined based on the relevance of the references to achieve the
study objectives. A systematic search was performed to identify all publications reporting on
EEE and Proposals for equine and human control and prevention. Four electronic databases
were searched: CAB Abstracts , Library of Institute of Tropical Medicine (EDS-ITM) ,
PubMed and ScienceDirect using the search terms "EEEV or EEE and Control and prevention"
applied for all article content. No restrictions were applied with respect to language, location,
and date of publication (the last search was performed on April 21, 2021). In addition,
additional manual searches of author collections of relevant peer-reviewed publications were
included. Duplicate references with the same information about what was found in the
corresponding searches were eliminated, and abstracts were also obtained for certain
references.
94
Result
Among the proposals for the control and prevention of Eastern Equine Encephalitis for equines
and humans in the country, we have:
Awareness of the disease in rural and wild areas: Explain the disease and its impact on the
environment through talks to the inhabitants of sectors at epidemiological risk (Coello et al.,
2020).
Measures to prevent the spread of EoE: The most important control measure is to reduce the
source of infection by biting the vector; therefore, insecticidal compounds (such as Detan) and
heavy clothing should be used to prevent transmission (CDC, 2021).
To make it known that migratory birds are amplifiers of EEEV: Migratory birds are the animals
that amplify the virus and carry the infection to places where there were no cases before. It is
necessary that migratory birds should be free and allowed to continue their passage through the
sector, without the need for them to be captured or killed for sporting or hunting purposes
(Reisen et al., 2010).
To teach about the hosts susceptible to EEEV and what are the warning signs in case of
suspected cases of EEE in the sector: Susceptible animals are birds, dogs, horses and humans,
in the latter two it produces encephalitis (Go et al., 2014). On the other hand, birds (Williams
et al., 1971) and equines (Monath et al., 1985) are considered sentinels of the disease (the first
cases always appear in them); therefore, they are indicators of suspected cases of wild
arbovirosis, and preferably, they occur in sectors with an immense ecological biodiversity
where migratory birds arrive (Santander, 2009, p. 11; Coello et al., 2020).
To make known, which are the most common hosts to investigate VEEE in the field: they are
Migratory birds, native birds, mosquitoes, rodents, domestic dogs, equines and humans (OIE,
2017, p. 16; Benvenuto et al., 2019).
To find out if there is viral circulation in the area: This is done through investigations or
inquiries about deaths and clinical characteristics of sentinel animals in the sector; also,
hamsters and chickens can be placed as sentinels, with the purpose of infecting them, in order
to then take samples from them and subsequently attempt viral isolation in cell cultures and
animals in the laboratory (OIE, 2017, p. 16).
To find out if any host is infected or has been infected by VEEE: Samples should be taken from
sentinel animals and antibodies for VEEE should be determined or viral detection should be
performed. To identify antibodies, the ELISA test is performed and for viral detection, the PCR
technique is used. ( Benvenuto et al., 2019) .
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April - June vol. 1. Num. 13 2022
Capture of migratory and domestic birds: Migratory and sector birds are caught with CDC-
type mist nets and domestic birds by hand pulse (OIE, 2017, p. 16).
Carry out mosquito trapping: It is performed with CDC type mosquito traps, supplemented
with CO2, placed from 6 pm to 6 am (Hoyos et al., 2015).
Placement of sentinel animals for field research: In field research for arboviruses, cages with
animals (chickens or hamsters) are also placed generally at a height between 1 to 2 meters
attached to trees and near the estuary, so that infected mosquitoes infect the animals through
bites (Hoyos et al., 2015; OIE, 2017, p. 16).
Rodent trapping: This is done with Tomehawk traps for larger animals such as opossums, and
Sherman traps for small animals (rodents) (Arrigo et al., 2010).
Procedure for taking samples from animals and humans: For domestic animals, permission
must first be requested from the owners of the animals; in the case of wild animals, permission
must be requested from the Foundation that protects the animals and the Ministry of the
Environment. In the case of humans, permission must also be requested. Prior consent, for
equines the blood sample is taken from the jugular vein, for dogs from the jugular, saphenous
or popliteal vein, and for birds from the jugular or wing vein. In humans, the blood sample is
taken from the median vein, following procedures described by the OIE, PAHO/WHO and
CDC.
Blood samples are conducive for serological studies and viral detection, but in cases of equine
and human encephalitis the best sample is Cerebrospinal Fluid or brain tissue (OIE, 2017, p.
16).
Attempted viral isolation: From a brain sample of the deceased equine by encephalitis, viral
isolation can be done in cell culture (BHK-21, Vero, C636 cells) where cytopathic effects are
evidenced; or intraparietal viral inoculation in 48-hour-old suckling mice, where after 3 days
we observed signs and symptoms of disease (OIE, 2017, p. 16; Benvenuto et al., 2019).
Diagnosis for VEEE in various hosts: Laboratory diagnosis is effective to determine the disease
in the area and to differentiate from other arboviruses. Therefore, two methods should be
followed: Indirect method (antibody detection) and direct method (viral detection) (OIE, 2017,
p. 16).
Indirect methods include: ELISA, Indirect Hemagglutination, Indirect Immunofluorescence,
and the confirmation of antibodies is performed by the method of Neutralization by Reduction
of the Number of Plates. It is important to mention that all arboviruses need to be confirmed
due to the intense cross-reactivity among them, because the epitopes (antigens) are very similar
(OIE, 2017, p. 16; Benvenuto et al., 2019).
96
Direct methods include: Viral Culture, Electron Microscopy, Direct Hemagglutination, Direct
Immunofluorescence and PCR (OIE, 2017, p. 16).
Training of health professionals is important in order to be prepared for suspected cases of
arbovirus (PAHO/WHO, 2017).
Periodic investigation in sites of epidemiological impact: It is recommended to investigate
direct and indirect viral activity in sentinel animals at least, every year coinciding with the
arrival of migratory birds in the sector (OIE, 2017 p. 16; PAHO/WHO, 2017).
How to acquire immunity for EEE in equines: In equines it is by vaccination. In contrast, in
humans there is no vaccine for the disease (OIE, 2017, p. 16).
Where to go in case of suspicious outbreaks: In case of suspicious cases, it is recommended to
inform the epidemiological surveillance systems of Agrocalidad, the Ministry of Public Health
of Ecuador and the Ministry of Environment (OIE, 2017; PAHO/WHO, 2017).
The control and prevention proposal exposed, about Eastern Equine Encephalitis for equines
and humans, is with the purpose of raising awareness about a possible introduction of this
disease in Ecuador and in the American continent; in this way, the present study allows to
contribute with knowledge about control and prevention of EEE and to avoid future outbreaks.
Therefore, when a suspicious case is registered, we can be alert to any warning signs of the
disease, in order to take all appropriate and effective measures to deal with the disease, as is
done in North American countries (Bingham et al., 2014; Gill et al., 2019; Morens et al., 2019).
The points suggested in this article are taken according to OIE (2017, p. 16) / PAHO and WHO
(2017) / and CDC (2020) criteria.
It is also important that the community is prepared for these cases, and inform the
epidemiological surveillance systems of the EEE in Agrocalidad, Ministry of Public Health of
Ecuador and Ministry of Environment.
Finally, it is transcendental to highlight that in the human and equine population there is a risk
of Eastern Equine Encephalitis, although it is currently in epidemiological silence and could
cause epizootics or re-emerging epidemics in a very short period of time.
Conclusions
A proposal was made for the control and prevention of Eastern Equine Encephalitis for equines
and humans in Ecuador, which can be used by the scientific community and especially for
communities living in wild places.
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April - June vol. 1. Num. 13 2022
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