Course 151 - Biological Health Hazards in Construction

Infectious Animals and Insects

These rabbits are being tested for rabies.

Many different poisonous and infectious insects and animals are found throughout the United States. Workers should be aware of these health hazards before starting work in a specific location.


Rabies is a viral disease caused by infection of the central nervous systems of wild and domestic animals and humans. The initial symptoms of human rabies resemble those of other systemic viral infections, including fever, headache, and disorders of the upper respiratory and gastrointestinal tracts.

Raccoons, skunks, foxes, and coyotes are the terrestrial animals most often infected with rabies in the United States. All bites by such wildlife must be considered a possible exposure to the rabies virus.

Leptospirosis (Weil's Disease)

Leptospirosis is a bacterial disease that affects humans and animals. It is caused by bacteria of the genus Leptospira. Weil's Disease is a severe form of leptospirosis in humans. You can contract it if you come into contact with the urine, blood, or tissue of animals or rodents that are infected with the bacteria. These may include: cattle, pigs, dogs, and rats.

The time between a person’s exposure to a contaminated source and becoming sick is 2 days to 4 weeks. Illness usually begins abruptly with fever and other symptoms. After the first phase (with fever, chills, headache, muscle aches, vomiting, or diarrhea) the patient may recover for a time but become ill again. Without treatment, Leptospirosis can lead to kidney damage, meningitis (inflammation of the membrane around the brain and spinal cord), liver failure, respiratory distress, and even death. For more information see the CDC's Webpage on Leptospirosis.

1. Which animal is most likely to carry rabies?

a. Domestic dog
b. Wild boar
c. Raccoon
d. Ferret

Safe Disposal of Rodents

Should this person be wearing gloves?

Safe disposal of rodents and proper cleaning and disinfection of rodent-inhabited areas are keys to minimizing exposure to the virus.

The Center for Disease Control specifically recommends following these steps for safe disposal and clean-up of dead rodents and/or rodent dropping:

  • Wear rubber gloves.
  • Thoroughly spray dead rodents, traps, droppings, and contaminated areas with a general household disinfectant.
  • Place disinfectant-soaked rodents into a plastic bag and seal it. Then place it into a second plastic bag and seal. If possible, burn or bury the bag or contact your local or state health department about other appropriate disposal methods.
  • Disinfect floors, countertops and other surfaces with a general household disinfectant.
  • Before removing the gloves, wash gloved hands in disinfectant, and then in soap and water. Thoroughly wash hands with soap and water after removing the gloves.
  • Disinfect all used traps, and then set them again or replace them.
  • Eliminate possible rodent nesting sites such as junk cars, old tires and trash piles. Do not leave animal food and water in feeding dishes overnight, and keep all food in rodent-proof containers.
  • Cut grass, brush and dense shrubbery within the immediate area of buildings.

2. After placing disinfectant-soaked rodents into a plastic bag and sealing it, what's the next step?

a. Place it in a second plastic bag.
b. Carefully place it in a disposal bin.
c. Call the animal control agency for pickup.
d. Dispose of the animal and wash your hands.

Tick-Borne Diseases

Tick-borne lyme disease is common.

Tick-borne pathogens can be passed to humans by the bite of infected ticks. Ticks can be infected with bacteria, viruses, or parasites. Lyme disease is the most commonly reported tick-borne diseases in the United States.

How do Ticks Get on a Person?

Ticks do not jump, crawl, or fall onto a person. They are picked up when your clothing or hair brushes a leaf or other object they are on. Ticks are generally found within three feet of the ground. Once picked up, they will crawl until they find a favorable site to feed. Often they will find a spot at the back of a knee, near the hairline, or behind the ears.

Many tick-borne diseases can have similar signs and symptoms. If you have been bitten by a tick and develop the symptoms below within a few weeks, a health care provider should evaluate symptoms before deciding on a course of treatment:

Some of the most common tick-borne diseases in the United States include:

  • Lyme disease - Most common in the Northeast. Spread by black-legged or deer tick.
  • Rocky Mountain Spotted Fever - Common in the Southeast. Can be fatal if not treated soon.
  • Ehrlichiosis - Common in the Southwest. Spread by the lone star tick.
  • Babesiosis - Common in Northeast and upper Midwest. Spread by deer tick.
  • Human Granulocytic Anaplasmosis - In Midwest, Northeast and Northern California.

The most common symptoms of tick-related illnesses are:

  • Fever/chills: With all tickborne diseases, patients can experience fever at varying degrees and time of onset.
  • Aches and pains: Tickborne disease symptoms include headache, fatigue, and muscle aches. With Lyme disease, you may also experience joint pain. The severity and time of onset of these symptoms can depend on the disease and the patient's personal tolerance level.
  • Rash: Lyme disease, southern tick-associated rash illness (STARI), Rocky Mountain spotted fever (RMSF), ehrlichiosis, and tularemia can result in distinctive rashes

3. What is the most commonly reported tick-borne disease in the United States?

a. Rocky Mountain Spotted Fever
b. Lyme disease
c. Ehrlichiosis
d. Babesiosis

Lyme Disease

Symptoms of Lyme Disease
This images shows a bulls-eye rash on the back and shoulder.
Click to Enlarge

As we mentioned earlier, Lyme disease is the most commonly reported tick-borne disease in the United States. U.S. workers in the northeastern and north-central States are at the highest risk of exposure to infected ticks. 70-80 percent of Lyme disease is passed to humans by the bite of black-legged ticks (also known as deer ticks in the eastern United States) and western black-legged ticks infected with the bacterium Borrelia burgdorferi. The Lyme disease bacterium normally lives in mice, squirrels, and other small mammals.

Victims will develop a "bulls-eye" rash. Other signs and symptoms may be non-specific and similar to flu-like symptoms such as:

  • fever
  • lymph node swelling
  • neck stiffness
  • generalized fatigue
  • headaches
  • migrating joint aches
  • muscle aches

Most cases can be successfully treated with antibiotics, especially if treatment is started early. However, some workers may have symptoms such as arthritis, muscle and joint pain, or fatigue for an extended period of time.

4. What is a sign that a co-worker may be infected with Lyme disease?

a. Tissue necrosis
b. Two distinctive red marks
c. White pustules
d. "Bulls-eye" rash

West Nile Virus (WNV)

The A. triseriatus mosquito is responsible for spreading West Nile virus (WNV).

West Nile virus is transmitted by the bite of an infected mosquito. CDC reports that in four out of five cases, persons infected with WNV show no symptoms. In almost 20% of the cases, infections result in very mild flu-like symptoms, called West Nile fever.

The typical time from infection to the onset of signs and symptoms is 3 to 14 days. Signs and symptoms of the milder West Nile Fever and more severe infection (West Nile encephalitis or meningitis) include:

  • Mild West Nile Fever - Headache, fever, tiredness, aches, nausea/vomiting, swollen lymph nodes, skin rash.
  • West Nile encephalitis/meningitis - All the above plus stiffness in neck, stupor, possible coma, tremors, convulsions, muscle weakness, paralysis, loss of vision

Protect yourself from vector-born tick and mosquito hazards with these precautions:

  • Wear light-colored clothes to see ticks more easily.
  • Wear long sleeves; tuck pant legs into socks or boots.
  • Wear high boots or closed shoes that cover your feet completely.
  • Wear a hat.
  • Shower after work. Wash and dry your work clothes at high temperature.
  • Examine your body for ticks after work. Remove any attached ticks promptly and carefully with fine-tipped tweezers by gripping the tick. Do not use petroleum jelly, a hot match, or nail polish to remove the tick.
  • Apply Picaridin or insect repellent with DEET to exposed skin.
  • Spray clothing with repellents containing DEET or permethrin. (Note: Do not spray permethrin directly onto exposed skin.)
  • Be extra vigilant at dusk and dawn when mosquitoes are most active.
  • Get rid of sources of standing water (used tires, buckets) to reduce or eliminate mosquito breeding areas.

5. How is West Nile virus transmitted?

a. The bite of an infected mosquito
b. The bite of an infected tick
c. Contact with surfaces infected with the virus
d. Inhalation of contaminated airborne virus

Venomous Snakes

Venomous Western Rattlesnake

Venomous snakes found in the United States include rattlesnakes, copperheads, cottonmouths/water moccasins, and coral snakes. Although rare, some workers with a severe allergy to snake venom may be at risk of death if bitten. It has been estimated that 7,000–8,000 people per year receive venomous bites in the United States, and about 5 of those people die.

It is important for employers to train their workers about their risk of exposure to venomous snakes, how they can prevent and protect themselves from snake bites, and what they should do if they are bitten.

  • Watch where you place your hands and feet when removing debris. If possible, don't place your fingers under debris you are moving. Wear heavy gloves.
  • If you see a snake, step back and allow it to proceed.
  • Wear boots at least 10 inches high.
  • Watch for snakes sunning on fallen trees, limbs or other debris.
  • A snake's striking distance is about 1/2 the total length of the snake.
  • If bitten, note the color and shape of the snake's head to help with treatment.
  • Keep bite victims still and calm to slow the spread of venom in case the snake is poisonous. Seek medical attention as soon as possible.
  • Do not cut the wound or attempt to suck out the venom. Apply first aid: lay the person down so that the bite is below the level of the heart, and cover the bite with a clean, dry dressing.

6. How high should your work boots be to decrease the chance of being bitten by a venomous snake?

a. At least 6 inches
b. At least 7 inches
c. At least 8 inches
d. At least 10 inches

Venomous Spiders

Top - Male Black Widow
Bottom - Brown Recluse

Venomous spiders found in the United States include the black widow and the brown recluse. These spiders can be dangerous to construction workers. These spiders occasionally find their way inside structures or buildings and can also present a risk to indoor workers.

  • Black Widow: Black widow spiders are found throughout North America, but are most common in the southern and western areas of the United States. They are identified by a red-colored hourglass mark on the underside (females) or on top (males). Only females are poisonous, injecting a potent neurotoxic venom that is 15 times more potent than that of the rattlesnake. Though venomous, the quantity of poison is so minute that death is rare, though the bite is painful.
  • Brown Recluse: The brown recluse spider, also known as the violin spider, is most commonly found in the Midwestern and Southern states. It is brown in color with a characteristic dark violin-shaped (or fiddle-shaped) marking on its head and has six equal-sized eyes (most spiders have eight eyes). Sometimes a bite from a brown recluse spider can go unnoticed, or maybe feel as slight as a pinprick. Usually, after 2–8 hours, there is ensuing severe pain, erythema, and localized tissue necrosis (death) due to the venom's proteolytic enzymes.

Workers can take the following steps to prevent being bitten by venomous spiders:

  • Inspect or shake out any clothing, shoes, towels, or equipment before use.
  • Wear protective clothing such as a long-sleeved shirt, long pants, hat, gloves, and boots when handling stacked or undisturbed piles of materials.
  • Minimize the empty spaces between stacked materials.
  • Remove and reduce debris and rubble from around the outdoor work areas.
  • Trim or eliminate tall grasses from around outdoor work areas.
  • Store apparel and outdoor equipment in tightly closed plastic bags.
  • Keep your tetanus boosters up-to-date (every 10 years). Spider bites can become infected with tetanus spores.

7. Which spider bite may cause severe pain and localized tissue necrosis (death)?

a. Black widow
b. Brown recluse
c. Brown widow
d. Wolfe spider

Stinging Insects

This is a typical wasps nests

Stinging or biting insects or scorpions can be hazardous to outdoor workers. Stinging or biting insects include bees, wasps, hornets, and fire ants.

The health effects of stinging or biting insects or scorpions range from mild discomfort or pain to a lethal reaction for those workers allergic to the insect's venom. Anaphylactic shock is the body's severe allergic reaction to a bite or sting and requires immediate emergency care.

Bees and Wasps

Bees and wasps (including paper wasps, yellow jackets and hornets) are most abundant in the warmer months. Wasps can be generally distinguished from bees by their lack of body hair and thinner, elongated bodies. Nests and hives may be found in trees, under roof eaves, or on equipment such as ladders.

Workers should take the following steps to prevent insect stings:

  • Wear light-colored, smooth-finished clothing.
  • Avoid perfumed soaps, shampoos, and deodorants and don't wear cologne or perfume.
  • Avoid bananas and banana-scented toiletries.
  • Wear clean clothing and bathe daily. (Sweat may anger bees.)
  • Wear clothing to cover as much of the body as possible.
  • Avoid flowering plants when possible.
  • Keep work areas clean. Social wasps thrive in places where humans discard food.
  • Remain calm and still if a single stinging insect is flying around. (Swatting at an insect may cause it to sting.)
  • If you are attacked by several stinging insects at once, run to get away from them. (Bees release a chemical when they sting, which may attract other bees.)
  • If a bee comes inside your vehicle, stop the car slowly, and open all the windows.
  • Workers with a history of severe allergic reactions to insect bites or stings should consider carrying an epinephrine auto injector (EpiPen) and should wear a medical identification bracelet or necklace stating their allergy.

8. In a worst-case scenario, what can a wasp bite result in?

a. Epinephrine response
b. Anaphylactic shock
c. Redness at the sting
d. Soreness and itching


Scorpion on a person's shoe

Scorpions usually hide during the day and are active at night. They may be hiding under rocks, wood, or anything else lying on the ground. Some species may also burrow into the ground. Most scorpions live in dry, desert areas. However, some species can be found in grasslands, forests, and inside caves.

Symptoms of a scorpion sting may include:

  • stinging or burning sensation at the injection site (very little swelling or inflammation)
  • positive "tap test" (i.e., extreme pain when the sting site is tapped with a finger)
  • restlessness
  • convulsions
  • unusual eye movement
  • staggering gait
  • thick tongue sensation
  • slurred speech
  • drooling
  • muscle twitches
  • abdominal pain and cramps
  • respiratory depression

Workers should take the following steps to prevent scorpion stings:

  • Wear long sleeves and pants.
  • Wear leather gloves.
  • Shake out clothing or shoes before putting them on.
  • Workers with a history of severe allergic reactions to insect bites or stings should consider carrying an epinephrine auto injector (EpiPen) and should wear a medical identification bracelet or necklace stating their allergy.

9. What should workers carry with them if they can have an allergic reaction to a scorpion sting?

a. A phone to contact emergency services
b. A bracelet displaying his or her blood type
c. An epinephrine (EpiPen) auto injector
d. A scorpion venom removal kit

Fire Ants

Fire ants are very aggressive.

Imported fire ants first came to the United States around 1930. Now there are five times more ants per acre in the United States than in their native South America. The fire ants that came to the United States escaped their natural enemies and thrived in the southern landscape.

Fire ants bite and sting. They are aggressive when stinging and inject venom, which causes a burning sensation. Red bumps form at the sting location, and within a day or two they become white fluid-filled pustules.

Workers should take the following steps to prevent fire ant stings and bites:

  • Do not disturb or stand on or near ant mounds.
  • Be careful when lifting items (including animal carcasses) off the ground, as they may be covered in ants.
  • Fire ants may also be found on trees or in water, so always look over the area before starting to work.

10. What is likely the cause if you are stung on the leg and after a day or two notice white fluid-filled pustules where you were stung?

a. You received a bite from a bee
b. You were stung by a wasp
c. You were stung by a scorpion
d. You were bitten by a fire ant

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In this module we discussed the symptoms of exposure to various infectious insects and animals. See if you can match the symptoms of exposure to the related infectious insect or animal.

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