Rift Valley Fever – Kenya

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 February 4, 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 November 19, 2020, and livestock deaths had symptoms of fever, headache, general weakness with or without nausea, epistaxis / hematemesis, and abdominal pain / diarrhea reported to Isiol County Department of Health. The first case of people was recorded in late November 2020 from the Sericho department in the suburb of Garbatulla. Deaths have been reported in Gafarsa and Erisaboru in the suburbs of Garbatulla, as well as Korbesi in the sub-county of Merti. On December 16, RVF was confirmed by PCR at the National Virology Laboratory (NVL), Kenyan Institute for Medical Research (KEMRI). As of February 4, 2021, a total of 22 human cases (12 confirmed positive) and 10 deaths (three confirmed positive) have been reported. Most of the cases were from the suburbs of Garbatulla, with the majority of cattle breeders, men and 13 to 70 years old.

Sheep and goats were also reported sick on November 19, 2020 in the Sericho sub-county, which is mostly pastoral. Communities in this area live in villages, and cattle graze in common pastures. Animal samples were tested for IgM and PCR in real time on RVF at the Central Veterinary Laboratory (CVL), Cabete, and the Regional Veterinary Research Laboratory in Garissa. The event was officially confirmed on January 7, 2021, and reported to the World Organization for Animal Health (OIE) on January 15, 2021 and later on January 22 and 29, 2021. As of January 27, a total of 20 livestock samples (19 sheep and 1 camel) was positive for RVF by IgM-capture ELISA and real-time PCR.

Mandera County

A patient from the village of Kalmalab, Mandera North sub-county fell ill after taking part in the slaughter of four sick camels. He was evacuated to a hospital in Nairobi with hemorrhagic symptoms on January 18th. He was later admitted to the intensive care unit with multiple organ failure. The RVF was confirmed on January 21 on NVL. He died on 22 January 2021. As of 4 February 2021, a total of 10 cases (2 confirmed RVF positive), including 1 death, were reported from Mandera North sub-county.

The village of Kalmalab is bordered by the Dawa River which broke through banks after rains in the Ethiopian highlands. An outbreak of RVF could be associated with this flood, as it increases the risk of zoonosis transmitted by mosquitoes. Livestock samples were submitted to CVL Kabeta for testing.

Murang County

Cattle with RVF syndromes (including bleeding and miscarriages) were first reported on December 29, 2020 in the Gatanga subdivision, Kihumbuini department. The first animal deaths were recorded on January 1, 2021. Samples were collected on the same farm on January 1, and RVF was confirmed on January 3 on CVL Cabeta using Elisa IgG / IgM testing. Several cases of suspected animals have been reported in the Ng’araria department in Kandara sub-county. No human cases were confirmed, however suspicious cases were found and samples of affected households were collected on January 25 for testing at NVL.

Garissa County

Samples of suspicious cattle (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 underway to determine the extent of the outbreak.

Livestock surveillance was initiated after the discovery of an RVF outbreak in Isiol. Attacks among animals were observed during this period. In December 2020, the results of CVL Cabeta taken from 120 cattle revealed 20 (19 sheep of which 10 died and 1 camel) positive cases of RVF confirmed by the Elisa IgM study. Further laboratory analyzes in human and livestock samples are underway.

Public health response

The WHO works closely with the Ministry of Health through the local health cluster, together with the FAO and RES, supporting the following public health activities in response to the outbreak:

• RVF outbreak research (determination of the extent of outbreaks, related risk factors, vector monitoring and ecology mapping)
• Inclusion of RVF outbreaks in weekly outbreaks of SitRep disease
• Training of health workers (strengthening the capacity to detect RVF cases and appropriate case management)
• Raising awareness through radio spots, printing and disseminating information, education and communication (IEC) materials
• Capacity building of county laboratories for conducting tests for RVF and other diseases
• Quarantine for animals
• Ante and post mortem inspections
• Ongoing epidemiological investigations
• Sensitization of community health volunteers, health workers and veterinarians
• Planning to update and review the RVF contingency plan (latest version 2014) and developing / updating the RVF SOP for the post-outbreak period.

WHO risk assessment

RVF epidemics are recurrent in Kenya, and there have been several RVF epidemics in the past (1998, 2006-2007, 2014, 2018). The current epidemic affecting humans and animals in the districts of Isiolo (Ewaso Nyiro), Mandera (Dawa) and Garissa is linked to river floods. There was no flood / rain in Murangi; outbreaks are around wetlands and quarry lakes. Contact with infected animals has been linked to human infection. Livestock farmers, farmers, slaughterhouse workers and veterinarians have an increased risk of infection. The counties of Isiolo and Garissa are pastoral communities (primarily sheep and goats) in which cattle graze in common pastures.

The start of the event began in Serichou, Isiolo County, around November 19, 2020. RVF epidemics were later recorded in the sub-accounts of Balambala and Ijara, Garissa district, on December 7, 2020, attributed to floods along the Ewaso Basin whose river erupted on its shores in early November. 2020. This then led cattle to migrate and graze along the wetlands of the nearby river bank. The scene is currently reported in four counties in Kenya. However, given the favorable environmental conditions (heavy rains and floods) that may increase the presence of disease vectors, with the uncontrolled movement of viremic animals (in search of water and pastures), there is an increased risk of spreading the disease to other parts within Kenya and neighboring countries. It should be emphasized that the outbreak of RVF will have a serious economic impact on this pastoral community that depends on livestock production. The last vaccination of animals against RVF was in 2018, but the exact coverage is not known. Although the country has local capacity, response measures remain insufficient. Vector control measures have not been implemented and a national vector control plan has yet to be developed.

The first confirmed case of COVID-19 was registered in Kenya on 12 March 2020. As of 8 February 2021, Kenya had reported 101,819 confirmed cases of COVID-19 and 1,779 deaths. The impact of the pandemic has led to a widespread lack of supplies needed to achieve an effective RVF response, such as personal protective equipment (PPE). Furthermore, monitoring and laboratory services officers generally gave priority to responding to COVID-19.

WHO advice

Rift Valley Fever is a zoonosis transmitted by mosquitoes and primarily affects domestic animals (such as sheep, goats and camels). Humans become infected by contact with viremic animals and their fluids (blood, etc.). Human cases often occur near livestock outbreaks in an environment conducive to mosquito vectors that transmit the virus to both animals and sometimes humans. Most human infections are the result of direct or indirect contact with the blood, body fluids, or tissues of infected animals. Awareness of risk factors for RVF infection, integrated vector control activities, and protective measures against mosquito bites are key to reducing infection and human mortality. Public health messages to reduce risk should focus on:

• Public awareness and public education about RVF
• Reducing the risk of human-to-human transmission resulting from unsafe animal husbandry and slaughter. It is recommended to wash hands, use gloves and other protective equipment when handling sick animals or their tissues or when slaughtering animals.
• Reducing the risk of human-to-human transmission resulting from unsafe consumption of raw or unpasteurized milk or animal tissue; animal products found in endemic regions RVF should be thoroughly cooked before eating or drinking.
• Reducing the risk of mosquito bites by carrying out vector control activities (eg spraying with insecticides and using larvicides to reduce mosquito breeding sites), using insecticides impregnated with mosquito nets, protective clothing and avoiding outdoor activities during vector weather bites.
• Because RVF attacks on animals precede human cases, establishing and strengthening existing surveillance activities is crucial in preventing and managing RVF epidemics. These include an early warning and detection system for animal health, environmental monitoring, case monitoring and other measures in line with the One Health approach.
• Routine vaccination of animals is recommended to prevent the outbreak of RVF. However, vaccination campaigns are not recommended during outbreaks, as this may enhance transmission among the herd by the needle spread of the virus.
• Restrict the movement of animals to reduce the spread of the virus from infected to uninfected areas
• Vector surveillance measures need to be implemented, together with the development of a national vector control plan.

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

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