Cattle Fever Ticks Reinvade the United States: What Has Allowed their Return?

Tom Koerner/USFWS

The previous post, Cattle Fever Ticks Make a Comeback in Texas, looked at the growing problem of these two species of disease-carrying ticks in the United States more than a half century after their elimination from all but a narrow buffer zone along the Texas-Mexico border.

 Significant changes have occurred in recent decades in Texas that have allowed the resurgence of these ticks, and the threat that they may reintroduce babesiosis (or cattle fever) to the US. This deadly animal disease is estimated to cost upwards of $1 billion every year if allowed to spread unimpeded in the US?

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Cattle Fever Ticks Make a Comeback in Texas

Cattle fever ticks were for the most part eliminated from the United States over 70 years ago. Now they are back and spreading well beyond the buffer zone established along the Texas-Mexico border designed to prevent their return. Techniques that succeeded in ridding the US of these dreaded ticks decades ago are no longer as effective at killing or even containing them.

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What Is Killing the Saiga Antelope?

Mother saiga and calf, from the Cherniye Zemly (Black Earth) Nature Reserve, Kalmykia, Russia.      Photo: Igor Shpilenok

When nearly one-half of Kazakhstan’s saiga antelope population died suddenly in May 2015, speculation followed that this unique animal was on the brink of extinction. The immediate cause of death was found to be the bacterial disease hemorrhagic septicemia. But something had to happen to ignite the disease outbreak in the first place, and precious few clues exist as to what this might have been.

The saiga have faced similar mass die-offs in the past and have displayed a remarkable capacity to recover. There is great concern for this critically endangered species, but there is also room for hope. A better understanding of the complex epidemiology of hemorrhagic septicemia in saiga and livestock will reinforce this hope.

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Are Biting Flies Important Disease Spreaders?

Horse fly (Tabanus spp.) mouthparts. The dark, middle projection is the labium, used by the fly to lap up fluids. The much-feared scissor-like cutting parts are enclosed within the labium and not visible here. The top protrusion, though dangerous looking, is one of two antennae.   Alan R Walker

Biting flies are feared around the world for their painful bites, inflicted on both animals and humans. Like houseflies, which have no piercing mouthparts, biting flies can spread disease-causing pathogens that hitchhike on the flies’ legs, abdomen, or mouthparts, transmitting disease from ill to susceptible animals. This effect is reinforced by their feeding habit of severing capillaries near the skin surface to drink the blood that pools there.

Given these characteristics, it is surprising that biting flies are not more important pathogen spreaders than they actually are. Many of the dozens of diseases they are suspected of spreading are based on having identified those pathogens somewhere on a fly in the past. But documented transmission by biting flies between animals has been rare, for several reasons.

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Uganda and the Obstacles to Foot-and-Mouth Disease Control

Ankole breed cattle near Lake Mburo National Park, Uganda.    Stephanie L. Smith

Uganda is one of numerous countries around the world to have signed on to the UN Food & Agriculture Organization’s Progressive Control Pathway, aimed at reducing and eventually eliminating foot-and-mouth disease (FMD) from livestock herds. When I witnessed an FMD outbreak in Uganda 8 years ago, control efforts there were hampered by lack of resources, poor infrastructure, and pastoralists wary of government attempts to intervene and whose social traditions and economic necessities often clashed with disease control measures.

While these barriers have not disappeared today, Uganda has made improvements that place it in a better position to overcome the losses generated by this disease. These obstacles are not unique to Uganda, and the lessons learned here offer valuable assistance to nearly all countries embarking on the pathway to FMD elimination.

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Venezuelan Equine Encephalitis: How Small Effects Lead to Big Consequences

The northeast coast of Colombia, focus of several major Venezuelan equine encephalitis outbreaks in people and animals.     Charles Hoots

After a trip to Colombia last November, I wanted to do a post on Venezuelan equine encephalitis (VEE), yet another zoonotic, mosquito-borne virus of the tropics. The northeast coast of Colombia, along with neighboring Venezuela, has been the focus of several outbreaks of VEE in the past. But the last major one occurred in the 1990s and I decided it wasn’t current enough to write a post on.

Right on cue, in December 2016 Colombian authorities announced a mass equine vaccination campaign and restrictions on horse movements into and out of Colombia’s Cesar Department in response to an as yet limited VEE outbreak there. Colombia’s caution is warranted, given the unpredictable nature of this disease that in the past has vanished for decades at a time, only to reappear with devastating effects just when it was about to be written off as gone forever.

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Central Asian Wetlands as Predictors of Avian Influenza Spread

Lake Uvsu-Nur area on the Russian Federation-Mongolian border. Detection here of highly pathogenic H5N8 avian influenza in wild birds this past spring led to (correct) warnings that the virus would likely spread to the Middle East, Europe, and Africa.  © Alexey Butorin/Greenpeace

Another highly pathogenic avian influenza (HPAI) virus is marching across Western Asia, Europe, and North Africa, killing domestic flocks and a number of wild birds, from India in the east to the Atlantic Ocean in the west.

This is the 4th wave of HPAI to sweep across large swathes of the globe in the past 11 years. The culprit this time around, an H5N8 virus, appeared in India in October and the Mediterranean basin in November 2016, leading so far to the deaths of hundreds of thousands of domestic birds and dozens of wild birds from over 30 species.

A potential silver lining to this unfolding story is that this particular H5N8 virus was first detected 4 months earlier, from a lake on the Mongolian-Russian Federation border. Prompt reporting of the find led to warnings by experts of a high likelihood of spread to exactly those regions affected so far.

Was the early warning a lucky break, or have we learned enough about HPAI epidemiology to make such predictions routine? The answer is a bit of both.

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Pandora’s Box? The Risks of Pathogen Escape from Laboratories

Laboratory procedures for working on dangerous pathogens has changed significantly over the past 40 years. Randal J. Schoepp

Laboratory procedures for working on dangerous pathogens has changed significantly over the past 40 years. Randal J. Schoepp, James Gathany

Pathogens are maintained in laboratories around the world for many reasons. They can be used to develop vaccines, to provide materials for diagnostic tests, or to study genomes, offering clues as to how pathogens may evolve so that we are better prepared to deal with them.

There is debate within the scientific community as to exactly what kinds of research should be done on especially nasty organisms commonly called Potential Pandemic Pathogens, such as the deadly SARS respiratory virus or highly pathogenic avian influenza viruses. Some believe the risks of escape, though small, are not worth taking as an accidental release could sicken or even kill millions of people, animals, or both.

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New World Screwworm Outbreak in the United States: Sterile Flies to the Rescue

New World screwworm maggots on an endangered Key deer. The injuries on rutting males are particularly vulnerable to the fly. Early infestations can be treated effectively in pets, livestock, and people. But identifying and treating infested wildlife is difficult. Charles Hoots

New World screwworm maggots on an endangered Key deer. The injuries on rutting males are particularly vulnerable to the fly. Early infestations can be treated effectively in pets, livestock, and people. But identifying and treating infested wildlife is difficult.             Charles Hoots

When the presence of New World Screwworm (Cochliomyia hominivorax) was confirmed in the Florida Keys in September 2016, it was the first non-isolated appearance of the parasite in the United States in over 30 years. While the devastation to endangered wildlife on this archipelago has been significant, if the fly spreads unchecked to the mainland it could result in losses approaching $1 billion annually.

The release of large numbers of sterile male flies is the only known method to eliminate established New World Screwworm (NWS) populations. Identifying the geographical extent of the invaders is the critical first step. The flies typically are not great wanderers and refuse to cross open water. But when those in Florida began turning up on nearby islands with no land links to neighboring islands, the sterile fly release campaign became that much more complicated.

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Avian Botulism Die-Offs: The Mystery Continues

Waterfowl spring migration in the United States. Avian botulism outbreaks can kill millions of birds in a single season. USFWS

Waterfowl spring migration in the United States. Avian botulism outbreaks can kill millions of birds in a single season.     USFWS

Late summer and fall are prime time for die-offs of ducks, geese, and other wild water birds due to the toxin that causes botulism. This year is no different in the northern hemisphere, with small outbreaks reported in Colorado and North Carolina in the United States, and France and possibly the UK in Europe.

Since waterfowl die-offs due to botulism were first reported little more than a century ago in western North America, the disease has spread to over 28 countries today, many only since the 1970s.  Periodic outbreaks leave hundreds of thousands to millions of birds dead.

Avian botulism appeared and accelerated in lockstep with the exponential growth in the human population, and in particular the latter’s altering of wetland ecosystems. But just how to explain this association is not easy. Unprecedented environmental changes over the past two decades have witnessed not an increase in, but rather an absence of mass avian botulism die-offs. While our understanding has improved, we are nevertheless little closer to predicting and controlling these outbreaks today than we were a century ago.

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