Rift Valley fever – Kenya

9 months ago 233

Rift Valley fever (RVF) has been reported in Kenya in humans in Isiolo and Mandera counties and in animals in Isiolo, Mandera, Murang’a and Garissa counties. As of 4 February 2021, there were a total of 32 human cases (14 confirmed positive), and 11 deaths (CFR 34 %).

Isiolo County

The event is believed to have started on 19 November 2020, with deaths among herders presenting with symptoms of fever, headache, general malaise with or without nausea, epistaxis/hematemesis, and abdominal pain/diarrhoea reported to the County Department of Health in Isiolo. The first human case was reported in late November 2020 from Sericho ward in Garbatulla Subcounty. Deaths have been reported in Gafarsa and Erisaboru within Garbatulla subcounty as well Korbesa in Merti subcounty. On 16 December, RVF was confirmed by PCR at the National Virology Laboratory (NVL), Kenya Medical Research Institute (KEMRI). As of 4 February 2021, a total of 22 human cases had been reported (12 confirmed positive), and 10 deaths (three confirmed positive). Most cases were from Garbatulla subcounty, with the majority being herders, male, and aged 13 to 70 years old.

Sheep and goats were also reported sick on 19 November 2020 in Sericho subcounty, which is mainly pastoral. The communities in this area live in villages and livestock are grazed in communal grazing areas. Animal samples tested IgM and real time PCR positive for RVF at the Central Veterinary Laboratory (CVL), Kabete and the Regional Veterinary Investigation Laboratory in Garissa. The event was officially confirmed on 7 January 2021 and reported to the World Organisation for Animal Health (OIE) on 15 January 2021 and later on 22 and 29 January 2021. As of 27 January, a total of 20 livestock samples (19 sheep and 1 camel) had tested positive for RVF by IgM-capture ELISA and real-time PCR.

Mandera County

A patient from Kalmalab village, Mandera North subcounty fell ill after he was involved in the slaughter of four sick camels. He was evacuated to a Nairobi hospital with haemorrhagic symptoms on 18 January. He was later admitted to the Intensive Care Unit with multiple organ failure. RVF was confirmed on 21 January at the NVL. He died on 22 January 2021. As of 4 February 2021, a total of 10 cases (2 confirmed RVF positive), including 1 death had been reported from Mandera North sub county.

Kalmalab village borders the river Dawa which broke its banks following rains in the Ethiopian highlands. The RVF outbreak may be associated with this flooding, as it increases the risk of mosquito-borne zoonosis. Livestock samples have been submitted to CVL Kabete for testing.

Murang’a County

Livestock with RVF syndromes (including bleeding and abortions) were first reported on 29 December 2020 in Gatanga subcounty, Kihumbuini ward. The first animal death was reported on 1 January 2021. Samples were collected from the same farm on 1 January and were confirmed RVF positive on 3 January at CVL Kabete using Elisa IgG/IgM testing. More suspected animal cases have been reported in Ng’araria ward in Kandara subcounty. No human cases have been confirmed, however suspected cases were traced and samples from affected households were collected on 25 January for testing at NVL.

Garissa County

Samples from suspected livestock (sheep and goats) were collected from Masalani, Ijara Subcounty and Balambala, Balambala Subcountrym on 20 December 2020 for testing and were confirmed positive for RVF on 22 December using Elisa IgM testing. Field investigations are ongoing to determine the extent of the outbreak.

Surveillance in livestock was initiated after the detection of the RVF outbreak in Isiolo. Outbreaks among animals were observed during this time period. In December 2020, results from CVL Kabete taken from 120 livestock revealed 20 (19 sheep out of which 10 died, and 1 camel) positive RVF cases confirmed by Elisa IgM testing. Further laboratory analysis are ongoing in both human and livestock samples.

Public Health Response

WHO is working closely with the Ministry of Health via the local health cluster alongside the FAO and OIE in supporting the following public health activities in response to the outbreak:

RVF outbreak investigation (determining extent of the outbreak, associated risk factors, vector surveillance, and ecology mapping) Inclusion of the RVF outbreak into the weekly disease outbreak SitRep Training of health care workers (capacity building on RVF case detection and appropriate case management) Raising awareness via radio spots, printing and dissemination of Information, Education and Communication (IEC) materials Building capacity of the County laboratories to carry out tests for RVF and other diseases Animal quarantine Ante and post-mortem inspections Ongoing epidemiological investigations Sensitization of community health volunteers, healthcare workers and veterinarians Planning of updating and reviewing the RVF contingency plan (last version 2014) and develop/update RVF SOP for the post-outbreak period.

WHO risk assessment

RVF outbreaks are recurrent in Kenya and there have been several RVF outbreaks in the past (1998, 2006-2007, 2014, 2018). The current outbreak affecting humans and animals in Isiolo (Ewaso Nyiro), Mandera (Dawa) and Garissa counties is associated with rivers flooding. There was no flooding/rainfall in Muranga; outbreaks are around swampy areas, and quarry lakes. Contact with infected animals was associated with human infection. Herders, farmers, slaughterhouse workers, and veterinarians have an increased risk of infection. Isiolo and Garissa counties are pastoral communities (primarily sheep and goats) where livestock are grazed in communal grazing areas.

The onset of the event began in Sericho, Isiolo county around 19 November 2020. RVF outbreaks were later reported in Balambala and Ijara Subcounties, Garissa county on 7 December 2020 that were attributed to flooding along the Ewaso Basin whose river burst its banks in early November 2020. This then led livestock to migrate and graze along the marshy areas of the nearby riverbank. The location of the event is currently reported in four counties within Kenya. Yet, given the favourable environmental conditions (heavy rainfall and flooding) that can increase the presence of disease vectors, along with uncontrolled movement of viraemic animals (in search of water and pasture), there is an increased risk of disease spreading to other parts within Kenya and to neighbouring countries. It should be highlighted that an RVF outbreak will have a severe economic impact on this pastoral community that is dependent on livestock production. The last animal vaccination for RVF was in 2018, but the exact coverage is unknown. Although the country has local capacity, response measures remain insufficient. Vector control measures have not been conducted and a national vector control plan has yet to be developed.

The first confirmed COVID-19 case was registered in Kenya on 12 March 2020. As of 8 February 2021, Kenya had reported 101 819 confirmed COVID-19 cases and 1,779 deaths.. The impact of the pandemic has led to a wide-spread shortage of supplies necessary to mount an effective RVF response such as Personal Protective Equipment (PPE). Furthermore, surveillance officers and laboratory services have largely prioritised the COVID-19 response.

WHO advice

Rift Valley fever is a mosquito-borne zoonosis primarily affecting domestic animals (such as sheep, goats, and camels). Humans get infected through contact with viraemic animals and their fluids (blood, etc.). Human cases often occur in proximity to outbreaks in livestock in an environment favourable for mosquito vectors that also transmit the virus to animals and sometimes to humans. The majority of human infections result from direct or indirect contact with the blood, bodily fluids or tissues of infected animals. Awareness of the risk factors of RVF infection, integrated vector control activities and protective measures against mosquito bites is essential in reducing human infection and deaths. Public health messages for risk reduction should focus on:

Public awareness and public education on RVF Reducing the risk of animal-to-human transmission resulting from unsafe animal husbandry and slaughtering practices. Hand washing, use of gloves and other PPE when handling sick animals or their tissues or when slaughtering animals is recommended. Reducing the risk of animal-to-human transmission arising from the unsafe consumption of raw or unpasteurized milk or animal tissue; animal products found within RVF endemic regions should be thoroughly cooked prior to eating or drinking. Reducing the risk of mosquito bites through the implementation of vector control activities (e.g., insecticide spraying and use of larvicide to reduce mosquito breeding sites), use of insecticide-impregnated mosquito nets and repellents, protective clothing, and avoidance of outdoor activity at peak biting times of the vector species. As outbreaks of RVF in animals precede human cases, establishing and strengthening existing surveillance activities are essential in the prevention and management of RVF outbreaks. This includes the early warning and detection surveillance system for animal health, environmental monitoring, case surveillance and other measures in line with the One Health approach. Routine animal vaccination is recommended to prevent RVF outbreaks. However, vaccination campaigns are not recommended during an outbreak as it may intensify transmission among the herd through needle propagation of the virus. Restriction of animal movement to reduce the spread of the virus from infected to uninfected areas Vector surveillance measures need to be implemented, in conjunction with development of a national plan for vector control.

WHO advises against the application of any travel or trade restrictions on Kenya or the affected area based on the current information available on this event.

For more information on Rift Valley fever, please see the link below:

WHO fact sheet on Rift Valley fever
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