News Scan for Dec 11, 2014

Testing horses for MERS-CoV
Plague through the years

No evidence of MERS-CoV infection found in horses

Researchers who tested more than 1,000 horses, donkeys, and mules in Spain and the United Arab Emirates (UAE) say they found no evidence of past infection with MERS-CoV, although they were able to infect horse cells with the virus in a lab.

Writing in Emerging Infectious Diseases, the authors, from Germany, Spain, and the UAE, note that camels can carry MERS-CoV (Middle East respiratory syndrome coronavirus) and are probably an important reservoir for it. Previous studies of goats, sheep, cattle, and horses have shown no evidence of MERS-CoV infection, but the single study of horses involved only three animals, they said.

MERS-CoV uses a receptor molecule called DPP-4 to enter mammalian cells, and the researchers say the human and equine versions of DPP-4 share greater similarity than the human and camel versions of it. They found that cells derived from horse kidneys could be infected with MERs-CoV in a lab culture, as evidenced by damage to the cells and viral replication.

To look for antibodies suggesting past infection with MERS-CoV, the team collected serum samples from 192 horses in the UAE, where MERS-CoV is endemic, and from 697 horses, 82 donkeys, and 82 mules in Spain, where the virus is not endemic. Using a two-step serologic testing approach, the team found no evidence of MERS-CoV antibodies.

"Although we did not find evidence for equid infections with MERS-CoV in this study, the general susceptibility on the cell culture level suggests that equids from MERS-CoV–endemic areas, such as Africa and the Arabian Peninsula, should be further investigated for possible infection with MERS-CoV," the authors conclude.
Dec 10 Emerg Infect Dis letter


Researchers note 3 epidemiologic eras for US human plague

US Centers for Disease Control and Prevention (CDC) researchers who analyzed human cases of plague since 1900 found they could be grouped into three distinct epidemiologic patterns by chronology: (1) outbreaks common but localized early on, (2) rapid geographic expansion with fewer cases in the middle years, and (3) sporadic cases, mostly in the Southwest, in more recent years.

Writing in Emerging Infectious Diseases yesterday, they summarized the characteristics of 1,006 plague cases from US Public Health Service lists and in more recent years from CDC data and other sources like state reports and peer-reviewed literature.

Infections were acquired in 18 states, and the median patient age was 29, with about two-thirds male. Among 913 cases with adequate documentation, 744 (82%) were of the bubonic form, 87 (10%) septicemic, 74 (8%) pneumonic, 6 (1%) pharyngeal, and 2 (<1%) gastrointestinal.

From 1900 through 1925, 496 cases were reported (49% of the total), or about 3.5 per year. Cases were restricted almost exclusively to port cities on the Pacific and Gulf coasts, and 90% occurred in California and Louisiana. Cases number fluctuated widely by year. The median age was 30.

The second period, from 1926 through 1964, accounted for only 42 (4%) of the cases, or about 1 case a year. Cases were distributed inland, with all but 1 in western states. Fifty-two percent of cases occurred in California and 29% in New Mexico. The median age of these patients was only 15, and 82% were male.

From 1965 through 2012, 468 cases (47%) were reported, with the vast majority in the Southwest. New Mexico accounted for 54% of cases, followed by Arizona with 14%, Colorado with 12%, and California with 9%. The median age was 28, and 57% of patients were male. Primary septicemic plague was more common in this period, accounting for 17% of all cases.

The authors conclude, "Plague is likely to continue causing rare but severe human illness in western states."
Dec 10 Emerg Infect Dis study

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