Venomous Critters of the Southwestern Deserts


Venomous Critters of the Southwestern Deserts

By Jeff DeBellis

Illustrations by T.B.R. Walsh

“Those who travel in desert places do indeed meet with creatures surpassing all description.”

–Cormac McCarthy, Blood Meridian

Deserts are generally inhospitable places. They’re either too hot, too cold, too dry, or too windy. Sandstorms, monsoons, and flash floods ravage the land. The plants are spiky and the animals are venomous. Nonetheless, people like to visit the desert. A lot of people. Because despite the downsides, deserts are beautiful.

There are three distinct hot deserts in the American Southwest – the Chihuahuan, the Sonoran, and the Mojave. The Chihuahuan Desert covers southern New Mexico, western Texas, the extreme southeastern corner of Arizona, and extends into the Mexican states of Chihuahua, Coahuila, and Durango. The Sonoran Desert extends from southern Arizona and southeastern California into the Mexican state of Sonora. The Mojave covers southeastern California, southern Nevada, northwestern Arizona, and a tiny corner of southwestern Utah. The boundaries of the three deserts are determined by the distribution of plant and animal species. In some cases, the individual deserts are bounded by mountain ranges that form “sky islands” of more temperate habitat. Hot deserts differ from cold deserts (like the Great Basin farther north) in that most of their precipitation comes in the form of rain, as opposed to snow.

Deserts are home to a startlingly wide variety of plants and animals that have adapted to the harsh conditions. The Chihuahuan Desert is one of the most biodiverse arid regions on Earth. Most desert animals are not actually venomous. Regardless, all wild animals should be appreciated only from a safe distance. The creatures that are venomous include reptiles, such as snakes and Gila monsters, and arachnids, including spiders, scorpions, and to a lesser degree, tarantulas. This article describes many of the venomous species that are native to the region.



Rattlesnakes live nearly everywhere in the United States, but they are especially abundant in the southwest. There are 36 species in the western hemisphere, 17 in the U.S., and 14 in the southwestern deserts. The most poisonous of these are the Mojave rattlesnake (Crotalus scutulatus), with an LD50 SC of 0.31 mg/kg, and the tiger rattlesnake (Crotalus tigris), with an LD50 SC of 0.21 mg/kg. The LD50, also known as the median lethal dose, indicates how much venom it takes for a snake to kill 50% of its prey. The lower the number, the more potent the venom. The “SC” refers to subcutaneous injection, which is the most common way that humans are exposed to the venom. For comparison, the timber rattlesnake of the Eastern United States has an LD50 SC of 2.25 mg/kg.

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Volume 29 Number 2

ISSN 1059-6518

Center for Disease Control (

World Health Organization (

Latest Zika Situation Report – 25, August 2016

Microcephaly, Guillain-Barré Sydrome, and congenital anomalies


  • An Emergency Committee was convened by the Director-General under the International Health Regulations (2005) on 1 February 2016. Following the advice of the Committee, the Director-General announced the recent cluster of microcephaly and other neurologic disorders reported in Brazil to be a Public Health Emergency of International Concern.
  • The Emergency Committee agreed that a causal relationship between Zika infection during pregnancy and microcephaly is strongly suspected, though not yet scientifically proven. All experts agreed on the urgent need to coordinate international efforts to investigate and understand this relationship better.
  • As of 25 August 2016, a total of 70 countries have reported autochthonous circulation of Zika virus. It has been found in all of Central and South America, except for Chile.
  • 11 countries have reported evidence of person-to-person transmission.
  • The geographical distribution of Zika virus has been steadily increasing since it was first detected in the Americas in 2015. Further spread to countries within the geographical range of competent disease vectors — Aedes mosquitoes — is considered likely.
  • 18 countries have reported an increase in the incidence of cases of microcephaly and/or Guillain-Barré syndrome concomitantly with a Zika virus outbreak.

The global prevention and control strategy launched by WHO is based on surveillance, response activities, and research.

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But wait, there is yet another reason why you do not want to get bitten by a tick.

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Volume 28 Number 4

 By Frank Hubbell, DO

A tick bite can spread various diseases, but, as it turns Read more


TOT headerISSN-1059-6518 Volume 27 Number 1

Makonde for “that which bends up”


Chikungunya is NEW to the Caribbean Islands

By Frank Hubbell, DO

Haiti: A 19-year old female presents at a rural clinic with a high fever, 104F, a fine, erythematous rash on her feet and lower legs that does not blanch with pressure, and body aches and pains, that have been quite painful for the past 4 days.

The remainder of her physical exam is normal.

Living in a rural community, she does not have screens on her windows, and she does not sleep under mosquito netting. As a result, she is commonly bitten by mosquitos.

 Recently, there has been an outbreak of both dengue and chikungunya in the area.


 A single-stranded RNA virus of the Genus Alphavirus, Family Togaviridae,

 the virus targets the cells that make up blood vessels. It is the destruction of these cells that causes the bleeding into the skin and the non-blanching hemorrhagic rash, thus the name hemorrhagic fever.

 The reservoir in nature is primarily humans.MarchApri08lWMN copy-18.1

 The vector that spreads the virus from infected human to human is the Aedes mosquito; A. aegypti and A. albopictus.

 The Aedes mosquito can also spread:


            Dengue – infects blood vessels- hemorrhagic


            Eastern Equine Encephalitis – infects the brain- encephalopatic


            West Nile Virus – infects the brain- encephalopatic


Yellow Fever Virus – infects blood vessels- a lethal hemorrhagic illness

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