Abstract

Laasa fever is zoonotic disease gotten by direct or indirect contact with infected rat fluid or excreta. The host (multi mammate rat) is widely dispersed across sub-Saharan Africa while the virus’ range seems to be limited to West Africa. This viral disease has a high tendency of becoming endemic in Nigeria as new cases are being reported annually since the first outbreak in the region.

Keywords

Endemic, Lassa fever, Nigeria, propensity

Introduction

Lassa fever is an acute haemorrhagic disease caused by a single stranded RNA virus which is in Arenaviridae family (World Health Organization, 2016). Being a zoonotic disease, rat (of the genius mastomys) is known as the animal reservoir of the virus. It can be gotten through direct or indirect contact with the infected rat excreta or via body fluid from infected person to uninfected person (Ajayi et al., 2013). Lassa fever is asymptomatic in many cases (about 80% cases) but in others can lead to chest pain, headache, diarrhoea, and sometimes can lead to coma and disorientation in later stages. It has an incubation period of 6 to 21 days (WHO, 2006).

Lassa fever is endemic in West Africa and about 300,000 to 500,000 cases occur every year. A high rate of seroprevalence has been reported in Guinea, Sierra Leone, Nigeria, and Liberia (Kerneis et al., 2009).

The virus affects both men and women in all age group. Individuals at risk include those living in rural and peri-urban areas where there are crowded living condition and poor sanitation. Health care workers are also susceptible to be infected with the virus if proper barrier infection and nursing control are not kept (Ogbu et al., 2007).

In Nigeria, this virus was first identified in Borno1969 and since then outbreaks have been reported in different parts of the country (Ehichioya et al., 2010). It is an endemic prone disease in Nigeria and has been estimated to have about 21% seroprevalence in the country (Inegbenebor et al., 2010). As noted by the Nigeria Centre of Disease and control, Lassa fever has up to 50% case fatality rate in Nigeria. (Centre for Disease and Control, 2016). The aim of this paper, therefore, is to provide an overview of Lassa fever in Nigeria laying emphasis on the epidemiology, risk factors, and the recommended prevention/control strategies at different levels to curb its further occurrences.

Trends of Lassa fever occurrences in Nigeria

From the first outbreak of Lassa fever in Nigeria (1969), there has been a continually reported case of the disease in the country (NCDC, 2016).

In 2012, a report by the Nigeria ministry of health shows that there were 989 cases with 112 deaths, 1195 Lassa fever cases and a total mortality of 39 in 2013 and in 2014, there was 989 cases with 36 deaths (Federal Ministry of Health, 2016). Subsequently from November 2015, there has been recurrently a case of Lassa fever in Nigeria and in January 2016, there was 172 confirmed cases including 83 deaths and recently in the month of April, 2016 about 3 deaths in Nasarawa state and 7 quarantined after being tested positive to Lassa fever (NCDC, 2016). Therefore, there are a total of 268 Lassa fever suspected cases and 138 deaths have been recorded in 2016 by the Nigeria Centre of Disease and Control (Federal Ministry of Health, 2016).

Since the onset of the outbreak in December, 2016 and as at 9 June 2017 there have been a total of 501 cases including 104 deaths. Of which 175 are laboratory confirmed cases including 63 all dead, 189 are being further classified (WHO, 2017.)

The latest outbreak was reported in December 2017, a total number of 107 suspected cases have been recorded in 10 states as shown in table 1. 61 confirmed cases, 16 deaths of which 10 were health care workers as at 21^st January, 2018 (NCDC, 2018).

These evidences however, have shown that Lassa fever has become endemic disease in the country unless strict measures are employed fast to fight this viral disease.

Table 1: The outbreak distributions of Lassa fever in Nigeria by States

States Year of outbreak

Borno Plateau	1969 1976
Anambara	1974
Aba/ Imo	1980;1989
Edo	1984; 1993-1994
Ebonyi/Ogun	2005
Edo, Nasarawa, Gombe, Kaduna, Plateau, Lagos Kaduna, Kebbi, Plateau, Taraba, Edo, Kogi & Ondo	2009 2010
Anambra, Bauchi, Borno, Cross-River, Ebonyi, Edo, Enugu, Gombe, Kaduna, Kano, Kogi, Nasarawa, Ogun, Ondo, Plateau, Rivers, and Taraba	December 2016
Anambra, Bauchi, Cross-River, Edo, Taraba, Nasarawa, Ondo, Plateau, and Kano	June, 2017
Edo, Ondo, Bauchi, Nasarawa, Ebonyi, Anambra, Benue, Kogi, Imo and Lagos	January 2018

Data gotten from the Nigeria federal ministry of health and NDCD (2016,2018)

What can be done to control and prevent further occurrences of Lassa fever in Nigeria

The control and prevention of infection is essential to reduce or avoid the transmission of diseases that are communicable. This requires a basic understanding on the disease epidemiology and its risk factors. To prevent the transmission of Lassa fever from host (rat) to human which is the primary transmission, contact must be avoided with the Mastomys rodents (Inegbenebor, 2010). Though this may be impractical due to the wide distribution of rats (Mastomys) in Africa and the control may also be difficult to achieve (Ehichioya et al., 2010). However, some strategies can be employed to control and prevent the spread of this vector and its virus in Nigeria.

At individual level

In most parts of Nigeria, rodents live with humans as they invade houses in search of food for survival (Tobin et al., 2015). This can be controlled by using rodent trapping and storing foods especially grains in a rodent proof containers. To prevent the rodents from entering the house, the home must be kept clean and garbage must be disposed far away from home. Mastomys rodent is known to live in bushes; therefore reduction in bush burning can also be helpful in controlling the rats invading people houses in search of other inhabitant.

Eating bush meats are very common in most parts of Nigeria especially in the rural areas where they are readily available and cheap. Due to the outbreak of Lassa virus, using “rodents” such as bush rats, rabbits and other bush meats as a source of protein in food should be discouraged.

Lassa haemorrhagic fever is a very contagious and virulent viral infection (Makinde, 2016). Thus, further transmission from person to person should be avoided when caring for a patient with the virus, this can be done by wearing gloves, protective garments and sterilization or preferably burning of the equipment used on the patient.

Community level

Health education – Awareness should be created in the communities especially in the rural communities where they have little or no access to information. This awareness should focus on how to reduce contact with rodents and how suspected cases can be isolated. This can include campaign, posters, newspaper publication, and all media platforms. The community members should be involved in all round procedures in order to achieve a sustainable Lassa fever control (Inegbenebor, et al., 2010). The food vendors should be targeted and educated on how to avoid food contaminated with rodents.

Vaccination – The most viable control measure for Lassa fever in population level is vaccination, however, there is no vaccine that is effective for the protection against Lassa fever currently (WHO, 2016).

Treatment

The antiviral drug that is effective in Lassa fever treatment is Ribavirin in the early stage of the illness but it may not be effective in post exposure prophylaxis (WHO, 2016). In contrast, a study done McCormick in 1986 established that Ribavirin can also be used at any point in the illness and is still effective. He further stipulated that the antiviral drug can also be used for post exposure prophylaxis (Ogbu et al., 2007).

Conclusion

From this essay it is clear that Lassa fever is a very important vector borne disease that cannot be overlooked because of its endemicity in Nigeria. Therefore early and proper investigation of the outbreak and putting effective prevention and control measure will aid in averting possible future outbreak. Provision of efficient laboratory capacity should be provided in all states of Nigeria for the confirmation of Lassa fever. There is also need to ensure early mobilization of resources and ensure effective coordination at all levels in the country involving local communities and media in the outbreak control strategies of Lassa fever in Nigeria.

References

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