LOCAL

Minnesota Zoo deer herd affected by mortal disease

Reindeer on display at the Minnesota Zoo have succumbed to the effects of Epizootic Hemorrhagic Disease (EHD) in recent weeks. 4 out of 8 animals held at Minnesota’s largest zoo have died since the first case erupted in August. This viral disease is not unknown within the state boundaries, and it has been present for more than a century in the U.S. It was first detected in Minnesota in 2012 in a cow farm and has been observed in both farmed deer and wild deer across the state since then. 

EHD is transmitted through infected female insects carrying the Epizootic Hemorrhagic Disease virus (EHDV) to susceptible individuals. Infection soon becomes systemic, as the virus is known for attacking blood vessels. After 5 to 10 days post-infection, infected individuals, usually white-tailed deer, show life-threatening external and internal hemorrhagic lesions that lead to sudden mortality in some individuals. 

The occurrence of EHD might result in massive local mortality events but it is unlikely to escalate to a widespread transmission within a whole population. This is because EHD only transmits through a vector that exhibits a seasonal occurrence, and mortality happens rapidly enough to avoid the presence of infectious individuals over time.

Recent studies have looked at environmental patterns affecting the occurrence of EHD. Severe drought events seem to correlate with the emergence of EHD cases in northern US states, where deer populations exhibit lower levels of immunity to EHD compared to southern states where EHD presence is more common. Since droughts might positively influence vector populations, we would expect to see a rise of EHD cases in new drought-prone areas where the vector and highly susceptible deer populations overlap under climate change scenarios.

NATIONAL

A novel virus linked to mussel’s disease

Estimates indicate the mussel population in the U.S. has plummeted more than 70% over the last century, as native mussels are suffering severe population declines or have gone extinct due to environmental pollution, habitat destruction, harvesting, and invasive species. However, massive mortality events have been occurring for the last decades, in which catastrophic population demise of over 90% of local populations have been observed. The causes of these mortality events remain unknown to scientists.

A monitoring project led by researchers from the US Fish and Wildlife Service (FWS), United States Geological Survey (USGS) and the University of Wisconsin-Madison discovered a virus that was more likely the potential cause of mussel mortality events. The virus, identified as a densovirus, was present in almost 70% of the collected dying mussels. Moreover, the microscopic tissue lesions documented by the research team support the idea of a densovirus infection. Previously, densovirus has been linked to mass mortality in other invertebrates, including shrimp, crayfish, and mosquitoes, causing lethargy and extensive tissue damage.

However, more evidence is required to definitively declare densovirus as the concrete cause of mortality events. Research is needed to understand potential factors that might confound the relationship between densovirus and mortality events, such as the presence of other pathogens, physiological stressors, and climate change. 

As mortality events affecting mussels have surged around the world, monitoring mussel population for pathogens associated with die-off is crucial to establish proper management strategies aiming to improve mussel conservation and control the occurrence of mortality events.

INTERNATIONAL

COVID-19 and the logistics of vaccine distribution

As the race to develop a safe and effective COVID-19 vaccine unfolds among pharmaceutical companies and countries, other components of the vaccine supply chain have been evolving to meet the requirement of what experts have termed “the greatest logistical endeavor of the recent years.” While research and development of a vaccine is a massive undertaking, mass manufacturing and distribution of the vaccine to all sectors of the global population is perhaps equally complex, especially during the ongoing pandemic.

A coordinated global strategy is required to appropriately produce and distribute vaccines around the world. Manufacturing plans are already being set up by pharmaceutical companies, including assembling raw supplies and production capacity to be prepared for mass production. However, a key choke point may be the logistics of transporting the product to distribution centers and then to medical facilities without losing the “cold chain”—a temperature-controlled supply chain to keep vaccines functional and safe.

The transport industry has experienced a reduction in the cargo capacity and price surges this year, which is going to have an impact on the delivery capacity in certain regions. Uncertainties surrounding the specific temperature requirements from the most promising vaccines hinder this planning, as differences in the temperature required can dramatically change the infrastructure needed.

Despite all the initial setbacks, the transport industry has been building up and strengthening their refrigeration and cargo capacity in the recent months. Nevertheless, governments, health organizations and industry still have to develop plans to make the distribution of the vaccine feasible and effective among areas where refrigeration infrastructure is underdeveloped and local institutions lack proper human resources and experience.

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Department of Natural Resources
Global Change Biology

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