Ebola Disease: an Emerging Zoonosis

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REVIEW ARTICLE Ebola Disease: An Emerging Zoonosis

Sunanda Pandey, Vandip D. Chauhan, B. C. Parmar* and J. B. Nayak

Department of Veterinary Public Health, College of Veterinary Science & Animal Husbandry, Anand Agricultural University, Anand-388001, Gujarat, India.

Abstract Ebola virus disease (EVD) is an infectious disease of humans and

other primates caused by ebola viruses. Five known virus species are

Bundibugyo ebolavirus, Reston ebolavirus , Sudan ebolavirus , Tai Forest ebolavirus and Zaire ebolavirus . Signs and symptoms typically start Corresponding Author: between two days and three weeks after contracting the virus with a fever, sore throat, muscle pain, and headaches followed with vomition, Dr. B. C. Parmar diarrhea and rash along with decreased function of liver and kidneys. The virus spreads by direct contact with blood, secretions, organs or other body Email: [email protected] fluids of infected wild animal or fruit bat or infected human or indirect contact with environment contaminated with such fluids. Fruit bats are

believed to be the normal carrier who is able to spread the virus without

Received: 07/03/2015 being affected by it. The diagnosis of EVD is confirmed by isolating the virus, detecting its RNA or proteins or Ag with an antigen-capturing ELISA Revised: 27/04/2015 or immunostaining, or detecting antibodies against the virus in a person's blood. No known effective treatment is available. Supportive therapy Accepted: 28/04/2015 includes maintenance of blood volume and electrolyte balance, management, nausea, fever , anxiety and secondary bacterial infection. Isolation of exposed animals is necessary with follow up of strict infection control procedures to prevent virus transmission. Health education and

awareness to high risk groups is important to prevent further human

exposure.

Keywords: EVD, Immunostaining, ELISA, Virus isolation and Fruit bats.

1. Introduction ebolavirus (originally Côte d'Ivoire ebolavirus ), and Ebola Virus disease (EVD) is a fatal infectious simply Ebolavirus formerly known Zaire ebolavirus emerging zoonotic disease and also known as Ebola (Hoener et al., 2012). Each species of the Haemorrhagic Fever (EHF). Till 2012, there was no genus Ebolavirus has one member virus, and four of case reported but with global travel, outbreaks in these cause Ebola virus disease (EVD) in humans Africa got spread to Asia (WHO, 2014). Ebola viruses except Reston virus which asymptomatically infects were first described after outbreaks of EVD in human and causes EVD in other primates (Spickler, southern Sudan in June 1976 and in Zaire in August 2014; CDC, October 2014). Zaire Ebolavirus is 1976. The name Ebolavirus is derived from Ebola the type species for Ebolavirus , and has the highest river in Zaire and the suffix virus denoting a viral pathogenicity and mortality rate of the Ebola viruses genus (Kuhn et al., 2010). This genus was introduced (WHO, 2014) and is also responsible for the largest in 1998 as the "Ebola-like viruses" (Netesov et al ., number of outbreaks of the five known members of the 2000; Pringle, 1998). In 2002, the name was changed genus, including the 1976 Zaire outbreak and the to Ebolavirus (Feldmann et al ., 2005; Mayo, 2002) . outbreak of 2014 with the most deaths. The genus Ebolavirus belongs to the family Filoviridae , order Mononegavirales and the members 2. Reservoir of this genus are called Ebolaviruses . The five The natural reservoir for Ebola has yet to be known virus species are named for the region from confirmed; however, bats are considered to be the most where each of them was originally likely candidate species (Chowell and Nishiura, identified: Bundibugyo ebolavirus , Reston 2014). Three types of fruit bats ( Hypsignathus ebolavirus , Sudan ebolavirus , Tai Forest monstrosus , Epomops franqueti and Myonycteris

Journal of Foodborne and Zoonotic Diseases | April-June, 2015 | Vol 3 | Issue 2 | Pages 19-22 © 2015 Jakraya Publications (P) Ltd Pandey et al…Ebola Disease: An Emerging Zoonosis torquata ) were found to possibly carry the virus 4. Clinical Signs and Symptoms without getting sick. Experimental inoculation of nonhuman primates often results in clinical signs after 3-5 days, although 3. Transmission the incubation period was reported to be as long as 16 Ebola is introduced in the human population days in some animals. Pigs developed a fever 4 days through close contact with the blood, secretions, organs after inoculation with Zaire ebolavirus (Spickler, or other body fluids of infected wild animal or fruit bat. 2014). In Human, Signs and symptoms typically start Besides bats, other wild animals include several between two days and three weeks after contracting the monkey species, chimpanzees, gorillas, baboons virus with a fever, sore throat, muscle pain and and duikers (SDS, 2014). Animals may become headaches. infected when they eat fruit partially eaten by bats Then, vomiting, diarrhea and rash usually follow carrying the virus (Gonzalez et al., 2007). Human to along with decreased function of the liver and kidneys. human transmission occurs only by direct contact with The disease has a high risk of death between 25 and 90 the blood or body fluids like vomit, faeces, sweat, percent of those infected with an average of about 50 saliva, mucus, tears, breast milk, urine and semen of a percent (WHO, 2014). person who has developed symptoms of the disease Nonhuman primates are severely affected, wild (Funk and Kumar, 2014; CDC, 2014; Drazen et al., chimpanzees and gorillas are often found dead. Clinical 2014) and indirect contact with environment signs observed in dying wild animals (of various contaminated with such fluids. Spread of Ebola by species) during ebolavirus outbreaks have included water, or food other than bushmeat, has not been vomiting, diarrhea, hair loss and emaciation, as well as observed (Chowell and Nishiura, 2014). No spread by bleeding from the nostrils. Nonhuman primates that are mosquitos or other insects has been reported. experimentally infected may develop fever, anorexia, Entry points for the virus include the nose, vomiting, diarrhea, dyspnea, and splenomegaly and mouth, eyes, open wounds, cuts and abrasions. Contact weight loss. A skin rash is common, although it can be with surfaces or objects contaminated by the virus, absent in some species, or in animals inoculated by particularly needles and syringes, may also transmit the certain routes. Hemorrhagic signs may include infection (Chowell and Nishiura, 2014). Ebola may be petechiae, bleeding into the gastrointestinal tract, or spread through large droplets if a person is splashed bleeding from puncture wounds and mucous with droplets by a highly sick person but such membranes. Shock and hypothermia are soon followed transmission through the air has not been reported to by death. African species of ebolaviruses are usually occur during EVD outbreaks (WHO, Aug 2014) and more pathogenic than Reston ebolavirus : the clinical airborne transmission has only been demonstrated in signs are more severe, hemorrhages are more common very strict laboratory conditions, and then only from and the mortality rate is higher (Spickler, 2014) pigs to primates, but not from primates to primates Piglets (approximately 5-6 weeks of age) (Chowell and Nishiura, 2014; Funk and Kumar, 2014). inoculated with Zaire ebolavirus developed a fever and Unlike humans and primates, pigs with Ebola virus respiratory signs, which progressed to dyspnea, disease get very high ebolavirus concentrations in their anorexia and lethargy, while less severe signs occurred lungs, and not in their bloodstream. Therefore pigs with in slightly younger piglets inoculated with the same Ebola virus can spread the disease through droplets in virus. Guinea pigs may have a fever and weight loss, the air or on the ground when they sneeze or cough but recover. No clinical signs have been reported in (Weingarten et al., 2012). The virus is able to survive infected wild bats, and experimentally infected bats on objects for a few hours in a dried state, and can remain asymptomatic. survive for a few days within body fluids. Dead bodies remain infectious; thus, people 5. Diagnosis handling human remains in practices such as traditional It depends on history and clinical signs of burial rituals or more modern processes such patients. Possible laboratory indicators of EVD as embalming are at risk. About 69% of the cases of includes a low platelet count; an initially decreased Ebola infections in Guinea during the 2014 outbreak white blood cell count followed by an increased white are believed to have been contracted via unprotected blood cell count; elevated levels of the liver (or unsuitably protected) contact with infected corpses enzymes alanine aminotransferase (ALT) and aspartate during certain Guinean burial rituals (Chan, 2014; aminotransferase (AST) and abnormalities in blood WHO, Oct 2014). Health-care workers treating people clotting often consistent with disseminated with Ebola are at greatest risk of infection. intravascular coagulation (DIC) such as a

Journal of Foodborne and Zoonotic Diseases | April-June, 2015 | Vol 3 | Issue 2 | Pages 19-22 © 2015 Jakraya Publications (P) Ltd 20 Pandey et al…Ebola Disease: An Emerging Zoonosis prolonged prothrombin time, partial thromboplastin 6. Treatment time, and bleeding time (Kortepeter et al., 2011). There is as yet no known effective licensed The diagnosis of EVD is confirmed by medication or vaccine (Choi and Croyle, 2013). isolating the virus, detecting its RNA or proteins or Ag Standard treatment currently consists of supportive with an antigen-capture ELISA or immunostaining, or therapy which includes maintenance of blood volume detecting antibodies against the virus in a person's and electrolyte balance via the oral or blood. Isolating the virus by cell culture, detecting the by intravenous route, management of pain, viral RNA by polymerase chain nausea, fever and anxiety (Feldmann and Giesbert, reaction (PCR) (Goeijenbier et al., 2014) and detecting 2011), prevention of developing bacterial infection and proteins by ELISA are methods best used in the early dialysis may be needed for kidney failure, stages of the disease and also for detecting the virus in and extracorporeal membrane oxygenation may be human remains. Detecting antibodies against the virus used for lung dysfunction (Richardson et al., 2010). is most reliable in the later stages of the disease and in those who recover (CDC, Aug, 2014). IgM 7. Prevention and Control antibodies are detectable two days after symptom onset Animals that may be infected with ebolaviruses and IgG antibodies can be detected 6 to 18 days after must be reported immediately, to protect humans who symptom onset (Goeijenbier et al., 2014). During an may be exposed and aid in controlling the outbreak. outbreak, isolation of the virus via cell culture methods Quarantine of nonhuman primates during importation is often not feasible. In field or mobile hospitals, the protects humans and healthy nonhuman primates from most common and sensitive diagnostic methods exposure to virus. During outbreaks, suspects and are real-time PCR and ELISA (Grolla et al., 2005). exposed animals should be isolated after confirmation Filovirions, such as EBOV, may be identified by their of the disease. Strict infection control procedures are unique filamentous shapes in cell cultures examined necessary to prevent virus transmission on fomites. with electron microscopy, but this method cannot Prevention of human exposure during diagnosis and distinguish the various filoviruses (Giesbert and eradication activities is vital, as humans are severely Jahrling, 1995). affected (Spickler, 2014). In humans, ebola viruses are most reliably Health education to high risk groups such as detected in the blood (including serum) during the Doctors, nurses, Veterinarians etc (Pal, 1997; WHO, acute-stage of the disease, but they may also be found 2014). Healthcare workers should use the personal in oral fluids and in some cases in urine, breast milk, protective wears (eg. gloves, gowns, masks, goggles) to semen, anterior eye fluid and other body fluids, and in prevent exposure to blood and body fluids (Spickler, many tissues including the skin. Skin biopsies may be 2014). All equipment, medical waste, patient waste and collected at post-mortem. Serological assays include surfaces that may have come into contact with body ELISA tests and IFA, but neutralization tests are fluids need to be disinfected. Burial practices should unreliable. Because the consequences of misdiagnosis avoid all contact with the body or fomites. (including false positive diagnosis) are severe, multiple techniques are used to confirm the infection whenever possible (Spickler, 2014).

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