TRANSMISSION OF EBOLA VIRUS ON ANIMAL AND HUMANS

CHAPTER ONE

INTRODUCTIO

BACKGROUND INFORMATION

Transboundary animal diseases may be defined as those epidemic diseases which are highly contagious or transmissible and have the potential for very rapid spread irrespective of national borders, causing serious socio economic and possible health consequences (FAO, 2004). They constitute only a small minority of the infectious diseases that affect livestock but are dreaded for their suddenness, acuteness, and the wide spread nature of the losses they can produce (Chris et al.,1999).

There are two major types of transboundary animal diseases- the emerging diseases and the zoonoses (OIE, 2012). According to Morens and Fauci 2013, Emerging diseases can be classified into newly emerging diseases and reemerging diseases. Reemerging and newly emerging diseases can be defined respectively as those diseases that are able to expand their epidemiological spectrum appearing in new geographical area, affecting new susceptible species which is usually associated with the acquisition of new genes by an existing microbe; and referring to a completely unknown pathogen which is detected for the first time. Newly emerging infectious agents do not arise spontaneously they must recently have come from somewhere, usually from animal infections, as occurred with HIV infection, Ebola, influenza and Severe Acute Respiratory Syndrome (SARS) (Morens and Fauci 2013). Zoonoses on the other hand are diseases or infections which are naturally transmissible from animals to humans. According to the National Center for Emerging and Zoonotic Infectious Diseases (NCEZID) 2013, approximately 75% of recently emerging infectious diseases affecting humans are diseases of animal origin and approximately 60% of all human pathogens are zoonotic.

Transboundary animal disease outbreaks can be attributed to increasing globalization due to better sea, land and air transport of people, animals and goods; normadism, transhumance and movement of refugees  and their animals away from wars and civil disturbances. Outbreaks are also attributed to changes in livestock production systems due to intensification and commercialization of livestock farming leading to the spread of livestock farming into new ecosystems such as tropical rain forests placing human communities and their farm animals into close contact with a completely new range of infectious diseases which may have previously only circulated in wild life reservoirs and may be completely unknown. Global warming and the decline in government veterinary services and other infrastructures are also factors that contribute to the increased outbreaks of transboundary animal diseases (Chris et al 1999).

According to World Health Organization (WHO) 2014, the Ebola virus outbreak was first recorded in Zaire (The Democratic Republic of Congo of Central Africa) in the year 1976. Outbreaks of Ebola virus disease with the exception of the Reston Ebola virus have mainly been restricted to Africa and its recent outbreak is classified as the largest ever in nearly four decades of history of the disease in terms of numbers of cases and deaths. The virus is highly virulent and contagious often consuming the population but government and individuals’ quick response to quarantine areas may help to contain an outbreak (WHO, 2014).

TABLE 1: SHOWING SOME EMERGING/REEMERGING ZOONOTIC TRANSBOUNDARY ANIMAL DISEASES (NCEZID, 2014)

DISEASES INFORMATION Middle East Respiratory Syndrome (MERS-Cov) It is caused by Novel Corona Viruses. First identified in April 2012 and has since been seen in 9 countries- France, Germany, Italy, Jordan, Qatar, Saudi Arabia, Tunisia, United Arab Emirates and United Kingdom with all cases having some connection with the Middle East either directly or indirectly. Basic information such as the natural host, route of entry and mechanism of transmission remains unknown and about half of the human cases resulted in deaths. Nipah virus encephalitis Emerged from bats and caused epizootic in herds of intensively bred pigs which then served as animal reservoir from which the virus was transferred to humans. Severe Acute Respiratory Syndrome (SARS) Caused by Corona viruses. Emerged from bats and spread into human population through person to person transmission then human movement. Influenza

a)   H5NI Virus

b)   H791 Virus

c)   H6N1 Virus

Transmitted from wild birds to domestic poultry then humans.

First reported in poultry in China in 2013. Human infection occurs after exposure to infected poultry or contaminated environments. 137 cases with 45 deaths have been reported. No cases outside China have been reported.

Commonly isolated from wild and domestic avian species with no human cases previously reported until May 2013 when the virus was isolated from a symptomatic 20-year old woman.

• OBJECTIVES

The objectives of this study are therefore:

1. To understand the nature etiology of the diseases and how it is manifested in both man and susceptible animals.
2. To review the various implications of the emerging/reemerging Ebola virus on livestock and human population.
3. To assess the possible ways by which the transboundary animal disease (Ebola) can be controlled.

TRANSMISSION OF EBOLA VIRUS ON ANIMAL AND HUMANS