Ahead of Print - Influenza D Virus Infection in Dromedary Camels, Ethiopia - Volume 25, Number 6—June 2019 - Emerging Infectious Diseases journal - CDC

Ahead of Print - Influenza D Virus Infection in Dromedary Camels, Ethiopia - Volume 25, Number 6—June 2019 - Emerging Infectious Diseases journal - CDC

Volume 25, Number 6—June 2019

Research Letter

Influenza D Virus Infection in Dromedary Camels, Ethiopia

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More articles on Influenza

Shin Murakami, Tomoha Odagiri, Simenew Keskes Melaku, Boldbaatar Bazartseren, Hiroho Ishida, Akiko Takenaka-Uema, Yasushi Muraki, Hiroshi Sentsui, and Taisuke Horimoto 

Author affiliations: University of Tokyo, Tokyo, Japan (S. Murakami, T. Odagiri, H. Ishida, A. Takenaka-Uema, T. Horimoto); Addis Ababa Science and Technology University, Addis Ababa, Ethiopia (S.K. Melaku); Institute of Veterinary Medicine, Ulaanbaatar, Mongolia (B. Bazartseren); Iwate Medical University, Iwate, Japan (Y. Muraki); Nihon University, Kanagawa, Japan (H. Sentsui)

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Abstract

Influenza D virus has been found to cause respiratory diseases in livestock. We surveyed healthy dromedary camels in Ethiopia and found a high seroprevalence for this virus, in contrast to animals co-existing with the camels. Our observation implies that dromedary camels may play an important role in the circulation of influenza D virus.

Influenza D virus (IDV) was first isolated from pigs with respiratory symptoms in the USA in 2011 (1). Epidemiologic analyses revealed that the most likely main host of IDV is cattle, because the seropositivity rate in these animals is higher than that for other livestock (2–4). In a recent report, dromedary camels (Camelus dromedaries) exhibited substantially high seroprevalence (99%) for IDV in Kenya (5), suggesting that this animal is a potential reservoir of IDV. We examined seroprevalence of IDV in dromedary camels in Ethiopia and in Bactrian camels (Camelus bactrianus) in Mongolia.

We collected serum samples from dromedary camels (n = 38; average age 4.3 years, range 1–13 years), goats (n = 20; average age 3.9 years, range 1–8 years), sheep (n = 20; average age 2.7 years, range 1–4 years), cattle (n = 15; average age 6.7 years, range, 1–11 years), and donkeys (n = 2; ages 1 and 6) from 2 herds in Bati district, Amhara region, and 1 herd in Fafen district, Somali region, Ethiopia. All animals were apparently healthy, shared the same pasturage during the day, and stayed in barns specific for each animal species at night. To detect influenza D infection, we titrated the serum samples by hemagglutination inhibition (HI) assay using 3 antigenically distinct influenza D strains from the National Center for Biotechnology Information (NCBI) database: D/swine/Oklahoma/1334/2011 (D-OK lineage; D/OK) (1), D/bovine/Nebraska/9–5/2013 (D/660-lineage; D/NE) (6), and D/bovine/Yamagata/10710/2016 (D/Japan-lineage; D/Yamagata) (7). For the HI test, we treated the samples with receptor-destroying enzyme (RDEII; Denka Seiken, http://www.keyscientific.comExternal Link) at 37°C for 16 h, followed by heat inactivation at 56°C for 30 min. We then reacted serially diluted samples with each virus (4 HAU) at room temperature for 30 min and incubated them with a 0.6% suspension of turkey red blood cells at room temperature for 30 min. The HI titer of each sample was expressed as the reciprocal of the highest sample dilution that completely inhibited HA. We considered samples with HI titer >1:40 positive, to eliminate nonspecific reactions at low dilutions (4,8,9).