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Table of Contents
LETTER TO EDITOR
Year : 2018  |  Volume : 11  |  Issue : 9  |  Page : 547-548

Enhanced surveillance and cohesive policies needed to tackle Rift Valley fever


School of Biological Sciences, The University of Nairobi, P.O BOX 30197-00100, Nairobi, Kenya

Date of Submission30-Jun-2018
Date of Decision03-Aug-2018
Date of Acceptance10-Aug-2018
Date of Web Publication27-Sep-2018

Correspondence Address:
Eunice A Owino
School of Biological Sciences, The University of Nairobi, P.O BOX 30197-00100, Nairobi
Kenya
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1995-7645.242313

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  Abstract 


Keywords: Aedes app, Rift Valley fever, Surveillance, Prevention, Kenya


How to cite this article:
Owino EA. Enhanced surveillance and cohesive policies needed to tackle Rift Valley fever. Asian Pac J Trop Med 2018;11:547-8

How to cite this URL:
Owino EA. Enhanced surveillance and cohesive policies needed to tackle Rift Valley fever. Asian Pac J Trop Med [serial online] 2018 [cited 2018 Oct 19];11:547-8. Available from: http://www.apjtm.org/text.asp?2018/11/9/547/242313

Dear editor,

There has been an upsurge in Rift Valley fever (RVF) outbreaks in Kenya in the recent past. Even as I write this letter, the country is experiencing an outbreak which was confirmed by the Ministry of Health on 8 June 2018[1]. The current outbreak was first reported in Wajir County on 2nd June but has currently spread to other counties and killed up to 26 people from the counties of Wajir, Marsabit and Siaya. Six other counties have also been identified as having the highest risk of an outbreak. These include Tharaka-Nithi, Garissa, Tana River, Lamu, Garissa, Kajiado and Baringo counties whereas Mombasa and Nairobi are on heightened alert[2].

RVF is a mosquito-borne viral zoonosis that infects both livestock and humans. It’s caused by RVF virus, a negative-sense, single-stranded RNA virus, family Bunyaviridae, genus Phlebovirus. In livestock, the disease is characterized by forceful abortions and perinatal mortality with small livestock like sheep and goats showing a higher susceptibility as compared to large ones like Zebu cattle and Camels. In humans, the illness manifests with influenza like symptoms with occasional cases of encephalitis, retinitis, and generalized haemorrhagic syndrome in less than 8% of the infected. The disease was first isolated in sheep in Naivasha district in the former Rift Valley Province of Kenya in 1930 and described in 1931[3]. Since then, RVF has expanded in geographical distribution with every outbreak[4], and this has been attributed to environmental factors like rainfall and temperature, the density and movement of livestock and the presence of competent vector species[5]. Up to the current outbreak, Kenya has suffered 25 outbreaks since 1931 with eleven of these considered to be severe national epizootics that affected more than 3 districts[4].

Outbreaks are associated with unusually heavy rainfall, high humidity and increased vegetation cover as a result of the warming up of the ocean surfaces of the Indian and the Pacific oceans. This leads to extensive flooding resulting in mass emergence of flood water Aedes mosquitoes, some of which are infected with RVF virus from infected drought resistant eggs[6]. The infected female adult Aedes spp initiates transmission to nearby animals including sheep, goats, cattle, and camels which serve as amplifiers, infecting more mosquitoes. Secondary vectors, mainly from the Culex, Anopheles and Mansonia species, may also take over the breeding sites and propagate RVF virus transmission to additional animals and humans resulting into outbreaks[5].

The current outbreak in Kenya follows another outbreak that occurred in November 2014 to January 2015 and a previous major outbreak that occurred in 2006/2007 that caused the death of more than 150 people and losses to the extent of US $ 32 million due to hospitalization and care for the sick, losses of animal herds, vaccination costs and trade bans/value chain ramifications[7]. Previously, in 1997-1998, another major outbreak occurred in 3 East African countries of Kenya, Tanzania and Somalia and affected over 100 000 people whereby more than 450 died in Kenya alone[8].

Outbreaks of RVF have also been reported in other African countries like Egypt in 1977-1979 which affected over 200 000 people and caused over 600 deaths[9], South Africa in 1951 where over 100 000 sheep died and half a million livestock suffered abortions[10] in Mauritania, Senegal, Sudan and Madagascar. The disease has also been reported in the Arabian Peninsula. Saudi Arabia and Yemen[11].

It’s therefore possible that failure to control a RVF outbreak could seriously impact veterinary and human health not only in Kenya but Africa, Middle East and the rest of the world. This could have far reaching economic consequences due to massive loss of livestock, consequent export embargoes, and significant human morbidity and mortality. To exacerbate the problem, RVF virus has been described as a high-impact trans-boundary pathogen with potential for bioterrorism[12].

Climatic modelling and RVF forecasting: Outbreaks of RVF in Kenya have been associated with heavy rainfall and flooding, high humidity and increased vegetation cover as results of El Niño-Southern Oscillation phenomenon[13]. Therefore, satellite images and weather/climate forecasting data could be used to predict an impending outbreak and thus initiate vaccination of livestock in time to avert impending epidemics. However, positive results can only be achieved if the predictions are taken seriously and the important steps taken in time.

Vaccination: Animal immunization not only prevents the transmission of RVF in livestock but it has been established that humans mainly get serious infections by the RVF virus from contact with fluids and secretions from infected animals[13]. Therefore, sustained animal vaccination programme could majorly avert outbreaks in humans too. However, immunization must be implemented prior to an outbreak to avoid intensifying the outbreak through the use of multi-dose vials and the re-use of needles and syringes.

Establishment of an active animal health surveillance system: This would help to detect new cases and could prevent and/or slow the outbreak by providing early warning for veterinary and human public health authorities to prevent spill overs from animals to humans[14]. Banning livestock movement and livestock markets: Restricting livestock movement and sale during outbreaks may slow the expansion of the virus from infected to uninfected areas.

Public health education and awareness: Awareness message focussing on risk reductions in terms of safe animal husbandry and slaughtering practices to reduce animal-to-human transmission should be prioritized during outbreaks. The use of impregnated mosquito nets, personal insect repellent if available and avoidance of outdoor activities that exposes individuals to infective bites should be encouraged.

Standard precautions by healthcare workers: Health care staff caring for patients with suspected or confirmed RVF should practise standard precautions governing the handling of blood (including dried blood) and all other body fluids, secretions and excretions (excluding sweat).

Vector control: Larviciding breeding sites is an effective form of vector control especially where breeding sites can be clearly identified and are limited in size and extent. The animals could also be sprayed with repellents to prevent mosquito bites.

Conflict of interest statement

The author declares that she has no conflict of interest.

 
  References Top

1.
WHO. Rift Valley fever-Kenya: Disease outbreak news, 18 June 2018. [Online]Available from: https://reliefweb.int/report/kenya/rift-valley-fever-kenya-disease-outbreak-news-18-june-2018[Accessed on 27th August 2018].  Back to cited text no. 1
    
2.
Daily Nation. Ministry races to curb Rift Valley fever as death toll hits 26. [Online]Available from: https://www.nation.co.ke/counties/wajir/Govt-rushes-to-curb-Rift-Valley-fever-/3444790-4627920-o96n0f/index. html[Accessed on 27th August 2018].  Back to cited text no. 2
    
3.
Daubney R, Hudson J, Garnham P. Enzootic hepatitis or Rift Valley fever. An undescribed virus disease of sheep cattle and man from East Africa. J Pathol Bacteriol 1931; 34: 545-579.  Back to cited text no. 3
    
4.
Murithi R, Munyua P, Ithondeka P, Macharia J, Hightower A, Luman E, et al. Rift Valley fever in Kenya: history of epizootics and identification of vulnerable districts. Epidemiol Infect 2011; 139(3): 372-380.  Back to cited text no. 4
    
5.
Sang R, Arum S, Chepkorir E, Mosomtai G, Tigoi C, Sigei F, et al. Distribution and abundance of key vectors of Rift Valley fever and other arboviruses in two ecologically distinct counties in Kenya. PLoS Negl Trop Dis 2017; 11(2). doi: 10.1371/journal.pntd.0005341.  Back to cited text no. 5
    
6.
Davies FG, Linthicum KJ, James AD. Rainfall and epizootic Rift Valley fever. Bull World Health Organ 1985; 63(5): 941-943.  Back to cited text no. 6
    
7.
Rich KM, Wanyoike F. An assessment of the regional and national socioeconomic impacts of the 2007 Rift Valley fever outbreak in Kenya. Am J Trop Med Hyg 2010; 83(2 Suppl): 52-57.  Back to cited text no. 7
    
8.
Woods CW, Karpati AM, Grein T, McCarthy N, Gaturuku P, Muchiri E, et al. An outbreak of Rift Valley fever in Northeastern Kenya, 1997-98. Emerg Infect Dis 2002; 8(2):138-144.  Back to cited text no. 8
    
9.
El-Akkad AM. Rift Valley fever outbreak in Egypt. October-December 1977. J Egypt Public Health Assoc1978; 53(3-4): 123-128.  Back to cited text no. 9
    
10.
Pienaar NJ, Thompson PN. Temporal and spatial history of Rift Valley fever in South Africa: 1950 to 2011. Onderstepoort J Vet Res 2013; 80: 384.  Back to cited text no. 10
    
11.
Al-Afaleq AI, Abu Elzein EM, Mousa SM, Abbas AM. A retrospective study of Rift Valley fever in Saudi Arabia. Rev Sci Tech 2003; 22(3): 867-871.  Back to cited text no. 11
    
12.
Peters CJ, Spertzel R, Patrick W. Aerosol technology and biological weapons. In: Knobler SL, Mahmoud AAF, Pray LA. (eds). Biological threats and terrorism: Assessing the science and response capabilities. Washington: National Academy Press; 2002, p. 66-77.  Back to cited text no. 12
    
13.
Anyangu AS, Gould LH, Sharif SK, Nguku PM, Omolo JO, Mutonga D, et al. Risk factors for severe Rift Valley fever infection in Kenya, 2007. Am J Trop Med Hyg 2010; 83(2 Suppl): 14-21.  Back to cited text no. 13
    
14.
Oyas H, Holmstrom L, Kemunto NP, Muturi M, Mwatondo A, Osoro E, et al. Enhanced surveillance for Rift Valley fever in livestock during El Niño rains and threat of RVF outbreak, Kenya, 2015-2016. PLoS Negl Trop Dis 2018; 12(4): e0006353.  Back to cited text no. 14
    




 

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