Skip directly to site content Skip directly to page options Skip directly to A-Z link Skip directly to A-Z link Skip directly to A-Z link
Volume 17, Number 7—July 2011

Rift Valley Fever in Ruminants, Republic of Comoros, 2009

On This Page
Article Metrics
citations of this article
EID Journal Metrics on Scopus

Cite This Article

To the Editor: Rift Valley fever (RVF) is caused by a Phlebovirus (family Bunyaviridae) transmitted by a wide range of mosquitoes (1). This zoonotic disease is present in Africa, the Middle East, and Madagascar. Infections by RVF virus (RVFV) in ruminants cause massive abortions in livestock and high death rates in young animals, which result in major economic consequences. Humans are infected by mosquito bites, contact, or inhalation of aerosols. RVF is frequently unapparent or mild for humans, inducing an influenza-like illness that occasionally leads to more serious complications such as hemorrhage, meningoencephalitis, retinopathy, or even death (2).

Cattle are socially important in Republic of Comoros because massive slaughtering occurs during traditional wedding ceremonies known as “Grands Mariages,” especially on the main island, Grande Comore. Because of low meat production (only 20,000 head of local cattle), a large number of live ruminants enter Grande Comore from Anjouan and Mohéli, the other 2 islands of the Republic, from Madagascar and Tanzania without quarantine or any other preliminary veterinary control.

We report results from a serosurvey of the ruminant populations on the 3 islands of the Republic of Comoros during the 2009 dry season (April–August). A total of 488 blood samples were collected from randomly selected sheep, goats, and horned cattle and sent to laboratory facilities in Mayotte to be tested by an RVFV immunoglobulin (Ig) G competitive ELISA (3). Fifty IgG RVFV-negative and -positive serum samples were randomly selected for confirmation by a seroneutralization assay using the reference method described in the World Organisation for Animal Health manual (4,5).

Of the 488 serum samples tested, 160 were positive for RVFV, for a seroprevalence of 32.8% (95% confidence interval [CI] 28.6%–36.9%). The 3 species were positive for IgG, with prevalence of 30.6% (95% CI 24.2%–37.1%) for cattle, 33.5% (95% CI 27.6%–39.3%) for goats, and 39.0% (95% CI 24.1%–54.0%) for sheep. Using a χ2 test, we found no statistically significant differences regarding species and gender, but more adults than young animals were seropositive for RVFV IgG (p<0.001). Significant differences in RVFV seroprevalence were found between islands (p<0.005), especially between Anjouan (26.6%; 95% CI 20.0%–33.3%) and Moheli (45.8%; 95% CI 31.7%–59.9%); p = 0.011). Of the 50 samples tested in seroneutralization, 31/31 (100%) of RVFV IgG ELISA-positive serum samples were confirmed as positive for RVFV (Table).

The serologic evidence of RVFV circulation in the ruminant population of the Republic of Comoros is in accordance with the epidemiologic situation described in other countries in the area. Actually, the serosurvey was implemented after the RVF outbreaks reported in several countries in eastern Africa in 2007 during El Niño rains (6). In August 2007, RVFV was detected in a young person from Comoros, and indigenous transmission of RVFV in Mayotte was confirmed in 2008 (7). RVF outbreaks were also reported in Madagascar during the 2008 and 2009 rainy seasons (January–May 2008 and November–March 2009) (8). To our knowledge, no circulation of RVFV in Republic of Comoros has been reported despite frequent legal and illegal movements of populations and goods between Republic of Comoros and eastern Africa, Mayotte, Madagascar, and the others islands of the area. With 1 of 3 ruminants having been in contact with RVFV, our results suggest that the human population in these islands have likely been widely exposed to this virus. However, several questions remain unanswered: Was RVFV recently introduced in the country? Has the virus settled down in a local reservoir for years without major clinical consequences before reemerging thanks to favorable conditions? Actually, no massive abortions in livestock or high death rate in young animals have been notified so far by the Comorian Sanitary Services. Therefore, the origin of infection is presently unknown because animals could have been infected on the island or in another country from where they have been imported.

Because live ruminants have been imported from neighboring countries for 20 years, the risk of introducing new diseases in the country is high. Despite efforts of the Comorian sanitary services, the Republic of Comoros is particularly vulnerable to pathogens intrusion. Blackleg (1970, 1995) and the contagious ecthyma (1999) were probably introduced into the country by live ruminants imported from Madagascar (9). Since 2002, importation of live animals from Tanzania has been common, increasing the risk of introducing continental pathogens or vectors as illustrated with outbreaks of East Coast fever in 2003 and 2004 in Grande Comore (10). RVFV circulation presented in this study is another example of the exposure of the Republic of Comoros to emerging pathogens and potentially bears major consequences for the local economy and for public health. The improvement of the Comorian veterinary services and the setting up of surveillance programs are essential to limit the risk of introducing devastating diseases in the area.



We thank the vice president in charge of the Ministry of Agriculture, Fisheries, Environment, Industry, Energy, and Handicraft for providing logistical assistance and laboratory facilities and all herders and their representatives from the Comorian Farmers National Federation for their collaboration. We are also grateful to the Departmental Veterinary Laboratory at Mamoudzou, Mayotte, particularly Stéphanie Maeder and Abdou Achirafi for performing ELISA.

This work was supported with Fonds Européens de Développement Régional funds from the European Union within the Project “Programme de Coopération Scientifique sur les Maladies Animales Emergentes dans l’Océan Indien.”


Matthieu RogerComments to Author , Sébastien Girard, Abdourahime Faharoudine, Mohamed Halifa, Michèle Bouloy, Catherine Cetre-Sossah, and Eric Cardinale
Author affiliations: Author affiliations: Centre for Scientific Research and Intelligence on Emerging Infectious Diseases in the Indian Ocean, Sainte-Clotilde, La Réunion Island, France (M. Roger, E. Cardinale); French Agricultural Research Center for International Development (CIRAD), Montpellier, France (M. Roger, S. Girard, C. Cetre-Sossah, E. Cardinale); CIRAD, Mamoudzou, Mayotte (S. Girard); Vice-President, Ministry of Agriculture, Fisheries, Environment, Industry, Energy and Handicraft, Moroni, Republic of Comoros (A. Faharoudine, M. Halifa); Institut Pasteur, Paris, France (M. Bouloy)



  1. Turell  MJ, Linthicum  KJ, Patrican  LA, Davies  FG, Kairo  A, Bailey  CL. J Med Entomol. 2008;45:1028.Vector competence of selected African mosquito (Diptera: Culicidae) species for Rift Valley fever virus. DOIPubMedGoogle Scholar
  2. Swanepoel  R, Coetzer  JAW. Rift Valley fever. In: Coetzer JAW, Thomson GR, Tustin RC, editors. Infectious diseases of livestock. Oxford (UK): Oxford University Press; 2004. p. 1037–70.
  3. Paweska  JT, Mortimer  E, Leman  PA, Swanepoel  R. An inhibition enzyme-linked immunosorbent assay for the detection of antibody to Rift Valley fever virus in humans, domestic and wild ruminants. J Virol Methods. 2005;127:108. DOIPubMedGoogle Scholar
  4. World Organisation for Animal Health. Rift Valley fever. In: OIE manual of diagnostic tests and vaccines for terrestrial animals, vol. 1, 5th ed. Paris: Office International des Epizooties; 2004. p. 185–94.
  5. Digoutte  JP, Calvo-Wilson  MA, Mondo  M, Traoré-Laminzana  M, Adam  F. Continuous cell lines and immune ascitic fluids pools in arbovirus detection. Res Virol. 1992;143:41722. DOIPubMedGoogle Scholar
  6. Outbreaks of Rift Valley fever in Kenya, Somalia and United Republic of Tanzania, December 2006–April 2007. Wkly Epidemiol Rec. 2007;82:16978.PubMedGoogle Scholar
  7. Sissoko  D, Giry  C, Gabrie  P, Tarantola  A, Pettinelli  F, Collet  L, Rift Valley fever, Mayotte, 2007–2008. Emerg Infect Dis. 2009;15:56870. DOIPubMedGoogle Scholar
  8. Andriamandimby  SF, Randrianarivo-Solofoniaina  AE, Jeanmaire  EM, Ravololomanana  L, Razafimanantsoa  LT, Rakotojoelinandrasana  T, Rift Valley fever during rainy seasons, Madagascar, 2008 and 2009. Emerg Infect Dis. 2010;16:96370.PubMedGoogle Scholar
  9. Timmermans  E, Ruppol  P, Saido  A, Onclin  M. Influence du marché international et des stratégies d’approvisionnement en viande sur les risques d’importation de maladies. Le cas de l’ecthyma en République Fédérale Islamique des Comores. 2000 [cited 2010 Dec 1].
  10. De Deken  R, Martin  V, Saido  A, Madder  M, Brandt  J, Geysen  D. An outbreak of East Coast fever on the Comoros: a consequence of the import of immunised cattle from Tanzania? Vet Parasitol. 2007;143:24553. DOIPubMedGoogle Scholar




Cite This Article

DOI: 10.3201/eid1707.102031

Related Links


Table of Contents – Volume 17, Number 7—July 2011

EID Search Options
presentation_01 Advanced Article Search – Search articles by author and/or keyword.
presentation_01 Articles by Country Search – Search articles by the topic country.
presentation_01 Article Type Search – Search articles by article type and issue.



Please use the form below to submit correspondence to the authors or contact them at the following address:

Matthieu Roger, CRVOI–CIRAD UMR 15, CYROI Technopole 2 rue Maxime Rivière Sainte Clotilde 97490, La Réunion, France

Send To

10000 character(s) remaining.


Page created: August 18, 2011
Page updated: August 18, 2011
Page reviewed: August 18, 2011
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.