World's Deadliest Animals

What are the world’s most deadly animals? While lions, ti¬gers, jaguars, sharks and grizzly bears inspire plenty of fear, the animals that wreak the most havoc are much smaller.

Dr. John Hildebrand, regents professor of neuroscience in the departments of neurology, entomology and cellular biology at the University of Arizona, shared his expertise on “The most danger¬ous animals in the world: Arthropod vectors of disease” at the John Gray Center on the campus of Lamar University on Tuesday, March 22.

Hildebrand spoke on everything from the Black Death — a widespread epidemic of bubonic plague that killed about a third of the population of Europe between 1347 and 1400 — to more modernly relevant diseases like Zika, West Nile and Chagas, a painful and deadly disease that causes damage to the heart and central nervous system and spread by the dime-sized kissing bug, named so because it targets the face of its victim.

So what is the most dangerous animal in the world?

“The mosquito is the most dangerous animal in the world, arguably,” Hildebrand said. “Mosquitoes are far and away the big¬gest problem.”

These little guys kill around 725,000 people a year, according to gatesnotes.com, a blog maintained by billionaire Bill Gates, who has donated more than $500 million through his non-profit foundation to combat mosqui¬to-borne diseases like malaria.

“Humans are the second most dangerous,” Hildebrand added. “They are responsible for a lot of human deaths (475,000 per year), but not near as many as mosquitoes.”

Mosquitoes aren’t a new problem, either.

“These have been a problem for animal life long before there were humans walking around,” he said. “Mosquitoes were there and they were making their business somehow — sucking blood.”

Of course, like humans who shoot and stab with guns and knives, it’s not the mosquitoes themselves that are dangerous, it’s what they carry.

“It’s what they transmit when they bite,” Hildebrand said.

Lymphatic filariasis, also known as elephantiasis, is caused by parasitic worms and spread through the bites of infected mosquitoes. While elephantiasis is not lethal, it renders people functionless. About 1.5 billion people in the world are at risk for the disease in about 83 countries. About 120 million people are infected and about 40 million people are severely disabled due to elephan¬tiasis, Hildebrand said.

“It wipes out the productiv¬ity of the people infected,” he said. “It jams up the lymphatic system. … You get grotesque enlargement of legs and other limbs and genitalia. It’s not a pretty sight. These people become essentially immobile, unable to do anything.”

Mosquitoes are also respon¬sible for the transmission of arboviruses such as yellow fever, chikungunya, dengue, Zika, West Nile and various other forms of encephalitis. Malaria does not fall into this category because the organism that causes malaria is not a virus but rather a protozoan.

“There are more than 500 known viruses in this fam¬ily, and all of these diseases are vectored (carried) by the same mosquitoes of the genus Aedes,” Hildeb¬rand said. “You have them flying around here (in Southeast Texas).”

Hildebrand said people are at risk for many of these diseases because there are no vaccines.

“We’ve seen a lot of press lately about Zika, which to my mind is good,” he continued. “It’s calling people’s attention to the fact that we still have a serious problem with vector-borne disease, and particularly mosquito-borne disease. People tend to be oblivious to that.”

And Texas specifically has been on high alert when it comes to Zika. Most recently, a second case of the virus was confirmed in March in Fort Bend County. The first case was confirmed March 2. Statewide, there have been at least 14 cases of Zika, including eight in Har¬ris County. The virus has been associated with a rise of micro¬cephaly, a type of birth defect. It has affected more than 4,000 babies in Brazil.

Other deadly animals that made Hildebrand’s list were snakes, which came in at third, killing 50,000 people a year. Dogs, surprisingly were listed at No. 4, killing 25,000 people a year, mostly due to rabies; tsetse flies, which carry sleeping sickness, a vector-borne disease affecting the nervous system and causing extreme lethargy and death, came in at No. 5, killing 10,000 a year. Assassin bugs or kissing bugs kill around 10,000 people annually, as well. They carry the protozoa Trypanosoma cruzi also called Chagas disease, which, if left untreated, can cause congestive heart failure. The insect’s feces contain the protozoa. The bugs defecate while they feed or soon afterwards. If the person rubs the feces into a break in the skin, he or she could become infected. Scratching the insect bite can introduce the feces into the body. Hildebrand became interested in doing research on the danger of kissing bugs in his home state of Arizona, and even contacted the National Institute of Health to try to receive fund¬ing for the research.

“We’re all taxpayers and we’re paying for the money NIH spends and yet we couldn’t get NIH interested in this problem,” he said. “They offered to fund research in Brazil or Peru, but not Arizona.”

The NIH told Hildebrand that they didn’t know whether there was any transmission of Chagas disease in the United States. But now we do.

Chagas disease has been noticed more in Texas in recent years.

From 2013 to 2014, 39 human cases of Chagas disease were reported, according to the Texas De¬partment of State Health Services; 24 were acquired in another country, 12 were locally acquired, and the location of acquisition was unknown for three.

The Texas Legislature passed a bill in 2015 that requires the Department of State Health Services to establish sentinel surveillance for emerging and neglected tropical diseases such as Chagas disease and could improve understanding of the disease risk in the state.

With the help of American Red Cross, Hildeb¬rand has since begun researching Chagas at the University of Arizona. He discovered that around 40 percent of the principal species of kissing bugs in the foothills around Tucson are carrying the Chagas parasite.

Freshwater snails are responsible for the deaths of 10,000 people a year because they carry schistoso¬miasis, a parasitic disease of the liver, gastrointesti¬nal tract and bladder. Schistosomiasis is transmitted by contact with contaminated fresh water inhabited by snails carrying the parasite.

Hippos, another surprise in the list, kill around 500 people a year. According to National Geo¬graphic, the hippo is the most dangerous mammal in Africa due to its extremely unpredictable nature and seemingly unprovoked attacks.

Some of the familiar faces of fear come in farther down the list — crocodiles (1,000), lions (100), wolves (10) and sharks, which only kill around 10 humans a year.

The Lamar University chapter of Sigma Xi and the Scientific Research Society hosted Dr. Hildebrand’s lecture.

— Kevin King

 

Category: