Credit ECDC
#18,067
While it may seem like piling on after a litany of reports of HPAI H5N1 and SARS-CoV in farmed mink (see here, here, here, here, here, here, here and here), we've research letter today - published last week in the CDC's EID Journal - on the spread of Severe Fever With Thrombocytopenia Syndrome (SFTS) in farmed mink in China.
Because fur farms can house thousands of animals in close quarters, the ability of diseases to spread rapidly and evolve is far greater than what might occur with other susceptible hosts - like companion animals (i.e. dog & cats) or Mustelids (ferrets, mink, weasels, etc.) in the wild.
While this risk may be greatest in mink, it also extends to other farmed animals (e.g. foxes, raccoon dogs, etc.), and is not limited to just HPAI H5 and coronaviruses (see here, here, and here).
Last summer, in PNAS: Mink Farming Poses Risks for Future Viral Pandemics, we looked at an excellent opinion piece penned by two well known virologists from the UK (Professor Wendy Barclay & Tom Peacock) on why fur farms - and mink farms in particular - are high risk venues for zoonotic diseases.
While considered as far less of a threat today than either COVID or avian flu, we've been following the spread of a tick borne Phlebovirus which causes SFTS for more than a dozen years.
The virus was first discovered in China in 2009, but has subsequently been found in Japan, South Korea and Vietnam - and in 2019 was detected for the first time in Taiwan. The fatality rate in humans has ranged from single digits to > 30%, depending on the region.
Although primarily spread ticks, there is evidence that the virus can also be transmitted from from animals-to-humans (see EID Journal Direct Transmission of SFTS from Domestic Cat to Veterinary Personnel), and from human-to-human (see Nosocomial person-to-person transmission of severe fever with thrombocytopenia syndrome) either through aerosols or close contact with infected body fluids.
Aerosol transmission of severe fever with thrombocytopenia syndrome virus during resuscitation
Nosocomial Outbreak of SFTS Among Healthcare Workers in a Single Hospital in Daegu, Korea.
Two months ago, we looked at a report from Japan's Institute for Infectious Diseases on that country's first confirmed case of Human-to-Human transmission of the virus; from an elderly patient to an attending doctor.
All of which brings us to the following EID report. I've only posted some excerpts, so you'll want to follow the link for greater details. I'll have a brief postscript after the break.
Research Letter
Outbreak of Natural Severe Fever with Thrombocytopenia Syndrome Virus Infection in Farmed Minks, China
Ying Wang1, Mingfa Yang1, Hong Zhou, Chuansong Quan, and Hongtao Kang
Abstract
We isolated severe fever with thrombocytopenia syndrome virus (SFTSV) from farmed minks in China, providing evidence of natural SFTSV infection in farmed minks. Our findings support the potential role of farmed minks in maintaining SFTSV and are helpful for the development of public health interventions to reduce human infection.
Severe fever with thrombocytopenia syndrome (SFTS) is an emerging disease caused by a novel tickborne bunyavirus, SFTS virus (SFTSV), which was first identified in China in 2009 (1). Outside of China, SFTS was subsequently reported in South Korea, Japan, Vietnam, Myanmar, and Pakistan and now poses a global health problem (2–6). SFTSV is an enveloped virus belonging to the genus Bandavirus, family Phenuiviridae, order Bunyavirales.
The virus has 3 single-stranded negative-sense RNA segments, large (L), medium (M), and small (S) (1). The Haemaphysalis longicornis tick is widely considered to be the primary transmission vector (7), but the natural animal hosts of SFTSV remain uncertain. Despite the high seroprevalence observed in various domestic animals in SFTSV-endemic regions, such as goats, cattle, dogs, pigs, chickens, and rodents, many of those animals do not show notable symptoms. Those infections were plausibly a result of SFTSV transmission from infected ticks (8).
We describe an outbreak of SFTS on a mink farm situated in Shandong, China. During late May through early July, 2022, >1,500 minks on this farm exhibited symptoms such as vomiting, diarrhea, and, in a small number, limb convulsions.
Most minks exhibiting clinical manifestations died of the disease (Figure 1, panel A). Clinical manifestations included loose stools, mesenteric lymph node enlargement, and hyperemia (Figure 1, panels B and C), consistent with typical enteritis symptoms. Treatment with multiple antibiotics was not effective, and mink enteritis virus infection was ruled out through testing with a colloidal gold immunochromatographic assay. Intestinal tissue samples from minks with diarrhea (n = 10) were collected and forwarded to the Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China, for testing.
(SNIP)
Previous research has shown the presence of antibodies to the nucleoprotein of SFTSV in farmed minks and suggested that minks were infected with SFTSV in China (10). In this study, we successfully isolated and identified an SFTSV isolate, named SD01/China/2022, in farmed minks in China.The symptoms of farmed minks in this case were consistent with SFTS symptoms, such as gastrointestinal disorders and central nervous system manifestations, which proved the occurrence of natural SFTSV infection–related fatalities in this population. Our findings reveal the threat of SFTS to the fur animal–breeding industry.Of note, phylogenetic analysis of the isolate indicated high homology with SFTSV strains in humans, suggesting that the viruses generally infected both humans and minks, further supporting the potential role of farm minks in maintaining SFTSV.
Farmed minks have potential for direct contact with humans and might serve as crucial amplifying hosts in the transmission of SFTSV. Further analysis of SFTSV infection in other captive fur animals, such as raccoon dogs and foxes, will be required to determine other key reservoirs for SFTSV. We recommend a focus on the registration of mink exposure for humans with SFTS-like illnesses, as well as increased measures to reduce SFTSV exposure risk.
Ms. Wang is a PhD candidate at Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China. Her primary research interests focus on the host–pathogen interactions of tickborne viruses. Dr. Yang is a research associate at Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China. His research interests focus on phylogeny, virology, and molecular epidemiology, especially for tickborne viruses.
Admittedly SFTS resides pretty far down our worry list, but over the past 3+ years we've seen a mutated COVID variant emerge and spillover into humans from mink, and last week we saw a risk analysis on a more transmissible mink-derived H5N1 virus, both illustrating the dangers inherent in fur farming.
There is, however, a sizable gap between recognizing a problem and fixing it.
We've long known of the dangers of live markets in Asia, and the bush meat trade in Africa, yet they both continue to thrive. To be fair, we aren't exactly setting a great example with testing of dairy cattle (and other livestock) for H5N1 here in the United States.
Hard decisions are, well . . . hard.
But they are likely to be far less difficult than the ones that come with another pandemic.
