Chapter 8: Zoonoses, Vectors, Pests, and Poisonous Plants

10. Schistosomiasis is a/an: (A) Water contact disease (B) Foodborne disease (C) Milkborne disease (D) Airborne disease

A

2. What are the peak seasons for rats to breed in temperature zones? (A) Spring and fall (B) Summer and winter (C) Winter and spring (D) Fall and summer

A

3. Which one of the following pesticides can be legally used in the United States by the public? (A) Diazinon (B) Silvex (C) 2,4,5,-T (D) None of the above

A

Plants and animals (pests)

Both plants and animals may be pests. Some pests contaminate food, cause discomfort or allergic reactions, and may poison or even attack humans. Some major categories of pests include vertebrates, marine invertebrates, anthropods, and plant pests. Many pests are also vectors and transmitters of zoonoses. For example, mosquitoes, in addition to spreading malaria, yellow fever, elephantiasis, and other significant diseases, are nuisances. Because mosquitoes bite people, they are also categorized as pests.

15. Many diseases and infestations have common names that can confuse the professional when referred to by lay individuals and often children. The term cooties refers to a/an: (A) Flea infestation (B) Infestation of bedbugs (C) Lice infestation (D) Infestation of flies

C

7. Which of the following is MOST effective for controlling ragweed? (A) Fenthion (B) Dieldrin (C) 2, 4-D (D) Petroleum oil

C

9. The interval between exposure to an infectious agent and the appearance of the first symptom is called the: (A) Lag time (B) Susceptible period (C) Incubation period (D) Primary period

C

Fleas (vector)

Certain species of fleas transmit various forms of plague, one form of which decimated Europe six hundred years ago. Bubonic plague is a highly fatal disease. Symptoms include a sudden high fever, mental disorientation, severe exhaustion and weakness, and large swollen lymph glands (called buboes) that are especially noticeable in the area of the flea bite. Person-to-person transmission through respiration, called pneumonic plague, may follow a bubonic case, and this latter form is even more likely to cause death.

12. An infected organism that does not exhibit symptoms during the spread of an illness is called a: (A) Reservoir (B) Parasite (C) Host (D) Carrier

D

13. The killing of an infectious agent outside the body by chemical or physical means is termed: (A) Detoxification (B) Deodorization (C) Destabilization (D) Disinfection

D

14. Rocky Mountain spotted fever is spread by: (A) Flies (B) Spiders (C) Cockroaches (D) Ticks

D

4. Poison ivy, poison oak, and poison sumac contain oleoresin that is found in all parts of the plant EXCEPT the: (A) Leaves (B) Flowers (C) Bark (D) Wood

D

5. Psittacosis is MOST commonly spread by: (A) Bats (B) Shellfish (C) Rodents (D) Pigeons

D

Marine pests

Jellyfish and their relatives may sting people who swim in the ocean. Gastropod mullusks can inject a poison into the hand of waders who try to examine them

Wild birds and feral pigeons

are occasionally serious enough nuisances that they need to be controlled. Pigeon droppings are an especially significant nuisance problem in many cities, where the droppings accumulate on buildings, ledges, and sidewalks, as well as on statues. Bird droppings are often associated with histoplasmosis. Once again, the REHS must discriminate between minor nuisances and serious problems when deciding whether to become involved.

Pests

are plants and animals that are objectionable to humans. Pests contaminate food, cause discomfort and allergic reactions, and may poison humans and animals. In other words, pests are nuisances.

Bats

are valuable for destroying flying insects such as mosquitoes. However, bats may harbor disease, and their droppings, urine, and ectoparasites may be objectionable. Bat-to-human or bat-to-pet contact during daylight hours is rare and should be suspect if it occurs, since the behavior of sick bats will include daytime activity or exposure. It is also common for feral dogs and cats, skunks, raccoons, squirrels, snakes, and some herbivores to become problems for homeowners, farmers, and ranchers. Occasionally a wild animal will escape from a private or public zoo. The REHS must use keen discretion in determining when and how to respond to these types of problems. Many animals, though perceived by some to be pests, may be endangered and legally protected. Efforts for their control should be coordinated with United States Department of Agriculture (USDA's) Animal Damage Control program and other concerned agencies.

Mites

are very small, sometimes microscopic, relatives of ticks and spiders. Some mites can cause an itching skin disease - scabies. The presence of these mites is most notable in daycare centers, preschools, and nursing homes - especially during the winter and spring. Cat mites are similar to scabies, but they normally live on cats and other animals. They can, however, infest and bite people. The nymphs of chigger mites attach to people walking through infected vegetation, and are more commonly encountered in the warmer and more humid areas of the United States.

Moths, beetles, weevils, flies, and mites

infest food. They contaminate it with their cast-off skins, body parts, and body exudates, as do ants and cockroaches. Some dermestid beetles also devour or damage carpet and paper. Termites can cause structural damage to trees, homes, buildings, and other wooden structures in many parts of the country.

Salmonella

species can be transmitted passively to humans by handling turtles, especially young ones. For this reason, several years ago the Food and Drug Administration (FDA) banned with the United States all commercial sales of turtles having carapaces less than 4 inches wide. Baby chicks and ducklings have also been implicated in transmitting this disease. The incubation period within the host may be as short as six hours or as long as three days. The infected person may then be communicable to others for several weeks. Many of the symptoms of food poisoning are often present, such as headache, nausea and vomiting, diarrhea, and stomach pains; in addition, a fever may be present.

Zoonoses

are infections or infectious diseases of vertebrate animals that can be transmitted to human beings.

Vectors

are insects or other anthropods that transmit infectious agents to humans

tularemia

Another zoonosis that occurs in rabbits and other mammals. It can be contracted by humans, especially by those handling raw, infected meat. tularemia can be transmitted directly as a zoonosis or through vectors such as deerflies and wood ticks. It is also transmissible in other ways, including drinking infected water and inhaling infected dust. Symptoms are varied, but many include a slow-growing ulcer, especially on the hand, accompanied by swelling of lymph nodes; or there may just be swollen and painful lymph nodes. Symptoms of pneumonia may occur if tularemia is contracted by inhaling dust that is infected with these bacteria.

Bed bugs

At this point in time, bed bugs are not known to transmit any diseases or are considered vectors, however, their bites can lead to other secondary infections. Bed bugs were once a common public health pest worldwide, which declined in incidence through the mid-20th century. Recently however, bed bugs have undergone a dramatic resurgence and worldwide there are reports of increasing numbers of infestations. Western Europe, the United States, and Australia have also been included in this trend. Bed bugs are wingless insects, roughly oval in shape, 4-5 mm long when fully grown, and are fast runners. They are rust brown in color and change to a deeper red brown following a blood meal. Bed bugs are dorsoventrally flattened and being thin means that they can hide in narrow cracks and crevices, often making detection very difficult. Being a cryptic species, bed bugs shelter in a variety of dark locations, mostly close to where people sleep. these include under mattresses, floorboards, paintings and carpets, behind skirting, in various cracks and crevices of walls, within bed frames and other furniture, and behind loose wallpaper. Bed bugs tend to stay in close contact with each other and heavy infestations are accompanied by a distinctive sweet sickly smell. Blood spotting on mattresses and nearby furnishings is often a telltale sign of an infestation. Adults can survive up to a year without blood, allowing infestations to persist through periods when properties are vacant. Side effects of bedbug bites include itchy body swellings. In rare cases - usually involving people living in poverty - severe infestations may lead to severe blood loss, due to the volume of feeding by hundreds or even thousands of bedbugs.

1. Rocky Mountain spotted fever is transmitted by: (A) Deerflies (B) Dog ticks (C) Deermites (D) Chiggers

B

11. A disease transmitted by birds and bird droppings is: (A) Dengue fever (B) Psittacosis (C) Tularemia (D) Hurine typhus

B

6. Hay fever is correctly referred to as: (A) Leguminosis (B) Pollenosis (C) Asthma (D) Sinusitis

B

8. The term "endemic" means: (A) Sporadic occurrence of an illness (B) Constant presence of an illness (C) All illnesses present at any one time (D) An unusually large number of persons with the same illness

B

Mosquitoes (vector)

Tens of thousands of people die annually around the world due to malaria, which is spread by mosquitoes of the genus Anopheles. Symptoms of the disease include fever, chills, sweating, and headache - and in serious cases, liver and kidney failure resulting in death. Some Aedes species transmit yellow fever. Symptoms are similar to malaria, but may also include nausea and vomiting and eventually jaundice. Less than 5% of victims in endemic areas die. However, often more than 50% of people not indigenous to the area where the disease is contracted will die. This is also true of people affected during an epidemic. Several Culex species, in addition to other species, spread various kinds of encephalitis. The usual onset of the disease includes a headache, weakness, muscle pain, and a variety of other symptoms. West Nile virus emerged in the United States in the New York metropolitan area in the fall of 1999. Since then, the virus, which can be transmitted to humans by the bite of an infected mosquito, has quickly spread across the country. Birds are the main reservoir of the virus. When a mosquito bites an infected bird, the mosquito can spread the virus by biting another bird or another animal, including a human. Since it first appeared, West Nile virus has spread rapidly westward, infecting birds, humans and horses. As of January 7, 2014, 48 states and the District of Columbia reported West Nile virus infections that occurred in 2013 in people, birds, or mosquitoes. A total of 2,374 cases of West Nile virus disease in people, including 114 deaths, have been reported to the Centers of Disease Control and Prevention for 2013. Of these, 1,205 (51%) were classified as neuroinvasive disease (such as meningitis or encephalitis) and 1,169 (49%) were classified as non-neuroinvasive disease.

Spiders

are a natural part of the environment, but they are a nuisance when they are inside buildings and homes. Infestations of the black widow, brown recluse, and aggressive house (hobo) spiders need occasional attention by the REHS because of the danger from their bites.

Cockroaches

are a well-known nuisance, the most common species in most parts of the United States being the American, Oriental, German, and the brown-banded. It is especially important that an REHS be able to identify these pests and know their habits. Termites, bedbugs, lice, and fleas are common pests, as are ants, wasps, and bees.

Rats

are associated with all three categories discussed in this chapter. Rats transmit diseases directly as zoonoses, including rat-bite fever; rats are one of the natural hosts of vectors of diseases, including plague; and rats are pests, both by their direct interaction with people and by their destruction of belongings. Worldwide, rats annually destroy or render unusable five times as much food as they consume. It is estimated that they cause nearly one billion dollars per year in damage in the United States alone. Mice, too, can harbor diseases, but they are primarily considered pests.

Weeds

are considered pests by the public, but the REHS will not be professionally interested in the aesthetics of weed control. Instead, the REHS should focus on plants that are poisonous or hazardous. Plants may be poisonous to human beings in three general ways: irritation caused by touching, toxicity caused by ingesting, and by an allergic reaction. Merely touching some plant species can result in irritation to the skin - the most well known being the spreading, ithcing welts of poison ivy, poison oak, and poison sumac. May people are also familiar with stinging nettle, a weed that causes a stinging sensation for several minutes. Many plants are, of course, poisonous if ingested. Hemlock, for example, is famous for its role in the execution of the Greek philosopher Socrates. Nightshade has very poisonous green berries that ripen to a red color. It is often found growing wild among cultivated pants. Among poisonous plants in the United States, some are even cultivated, including dumb cane (elephant's ears), castor beans, and larkspur. Occasionally, poisonous mushrooms are mistakenly harvested.

Lice

belong to the insect order Anoplura and Mallophaga. All known members are wingless parasites of warm-blooded animals. Lice from the two insect orders differ considerably in structure and feeding habits. Anoplurans have sucking mouthparts and feed on blood, while Mallophagens have chewing mouthparts and feed on skin scales and secretions. Because all lice are parasitic and spend virtually their entire life cycle on the host, it becomes a medical issue and treatment of host is involved. The common sucking lice examples are Body Louse, Crab Louse, and Heal Louse. The REHS must determine the existence of lice infestation and recommend medical attention.

Rabies

is an example of a zoonosis in that this virus is transmitted directly to people from a mammal having the disease itself. Animals throughout the world that are most often implicated in transmission of rabies to human beings include bats and most members of the order Carnivora, that is, the dog, cat, and weasel/skunk families. However, many other kinds of mammals are also transmitters. Rodents and rabbits are an exception and are rarely infected. The disease is transmitted to humans in virus-containing saliva that is introduced into a bite or scratch from a rabid animal. Airborne transmission has also occurred in caves harboring large numbers of bats. The incubation time in a person is usually from two to eight weeks, though both shorter and longer time periods have been noted. Symptoms in humans are varied but often include headache, fever, and weakness, followed by muscle spasms or paralysis and difficultly in swallowing. Death is often caused by paralysis of the breathing muscles.

Flies

make up one of the largest groups, with some of the more important biting or sucking pests being: houseflies, black flies, horseflies, deerflies, midges, and mosquitoes. Important nonbiting fly pests include gnats, fruit flies, and blowflies and flesh flies, whose maggots occasionally become parasites on humans, a condition called myiasis.

Mollusks (vector)

not usually classified as vectors, they transmit diseases in ways similar to those described for vectors. One example is a species of infected snail that, when eaten raw, can transmit liver flukes.

Mechanical transmission (vectors)

of infection is the passive carrying of disease organisms. With this method, infectious agents may be carried in two ways: either on the surface of the athropod or by its ingestion of the microorganisms. there is no further development of the disease organisms within the arthopod prior to transmission to humans. For example, when a fly walks on animal feces, some of the germs adhere to its hairs, bristles, and body. These germs can then be easily transmitted to humans.

Biological transmission (vectors)

of infection occurs when the microorganism multiplies or undergoes a cyclic development period within the host. For example, for a mosquito to transmit malaria, it must belong to one of the species of the genus Anopheles, and the malarial protozoan must be at a certain stage of its development in the host.