Pathogens and Disease

Question 1

Define pathogen and give examples

Answer 1

infectious, disease-causing agents. A pathogen causes disease.

Ex: Viruses, bacteria, fungi, parasites.

Question 2

Define disease and give examples

Answer 2

a condition in the body that impairs normal functioning, which can be caused by various agents, including infection, genetic defect, or stress.

Ex: The body’s reaction to injury

Question 3

Define infectious disease

Answer 3

diseases caused by tiny organisms (microorganisms), which are transmitted between animals.

Question 4

Define noninfectious disease

Answer 4

diseases not caused by organisms

Question 5

Define parasite

Answer 5

an organism that lives in or on another organism and benefits by deriving nutrients at the host’s expense; they can lead to disease in a host by
(1): acting as a vector that spreads pathogens.
(2): causing irritation.

Question 6

Define ectoparasite and give examples

Answer 6

a parasitic organism that lives on the outer surface of its host.

Ex: Mites, fleas, lice, ticks, etc.

Question 7

Define endoparasite

Answer 7

a parasitic organism that lives inside the host.
Ex: Tapeworms

Question 8

Define infection

Answer 8

a pathogen is present in an animal; however, the animal can be infected without exhibiting the disease

Question 9

Define exposure

Answer 9

the animal was previously exposed to a pathogen; the animal can be either (1) currently infected or (2) have cleared the pathogen and is no longer infected.

Question 10

Define seroprevalence

Answer 10

measures what proportion of the population has been exposed to a pathogen, does not mean that the animal is currently infected; animals might have already cleared the pathogen and now exhibit immunity.

Question 11

Define reservoir

Answer 11

domestic or wild animal populations that maintain a pathogen and can spread it within and between species

Question 12

Define spillover

Answer 12

when a pathogen is maintained in a reservoir species, and it spreads to other species.
Ex: Ebola, Plague, Hantavirus

Question 13

Define enzootic

Answer 13

chronic (always present, typically at lower levels) occurrence of diseases in wildlife populations

Question 14

Define epizootic

Answer 14

sudden unexpected outbreaks of disease in wildlife populations.

Analogous to an epidemic in human populations.

Question 15

Define zoonotic disease and give examples

Answer 15

Pathogens that are transmitted from wildlife to humans and cause disease.

Ex: Lyme disease, Rocky Mountain spotted fever, Hantavirus, Plague, Rabies.

Question 16

Explain the life history of lyme disease. What are the roles of small mammals and deer in the cycle? What stage of deer tick is most likely to infect humans? Why?

Answer 16

1. Adult females drop off host to lay eggs.
2. eggs hatch into six-legged larvae
3. Larvae attach to and feed on first host and may acquire B. burgdorferi (lyme disease)
4. Larvae molt into nymphs after leaving first host
   - Infected nymphs feed on humans, transmitting B.burgdorferi
5. Nymphs attach to and feed on second host and may acquire B. burgdorferi
6. Nymphs molt into adults after leaving second host
   - infected adults feed on dogs and sometimes humans, transmitting B. burgdorferi
7. Adults attach to the third host for feeding and mating

Question 17

How does changing landscape patterns affect patterns of lyme disease?

Answer 17

With increasing habitat fragmentation, the size of habitat patches decreases. As habitat patch area increases, the density of infected ticks decreases. More fragmentation - more infected ticks

Question 18

How is the distribution of lyme disease expected to spread within the next 50 years?

Answer 18

By 2080, lyme disease could spread throughout most of the eastern half of the US

Question 19

Explain the case study of brucellosis in cattle, bison, and elk. Why are bison the target for management when elk also can be infected by brucellosis?

Answer 19

Brucellosis is a disease caused by the bacteria Brucella.
It originated in cattle and can cause abortions.
Cattle transmitted brucella to bison, elk, and other cervids (spillover).
Ranchers are concerned that bison (reservoir) will act to spillover brucellosis back to cattle and 60% seroprevalence of brucella is in bison.
Bison migrate outside of yellowstone each year and can potentially encounter cattle.
Elk can get brucellosis but it is much less common than bison.

Question 20

Describe chronic wasting disease and its impact on ungulate populations.

Answer 20

an always fatal, neurological disease of the deer family caused by prions (transmissible spongiform encephalopathies) that alter proteins.

Can be transmitted directly and indirectly.
No cure or vaccine.
Leads to lower survival for CWS positive mule deer populations.

Question 21

What is notoedric mange? Since it tends to infect immune suppressed animals, what is causing carnivores to be widely exposed in urban California? What are the impacts to felid populations?

Answer 21

Notoedric mange: caused by ectoparasite mite that burrows into the animals skin and causes intense itching and scratching, leading to hair loss and skin wounds.

Carnivores consuming small mammals that have been exposed to anticoagulant rodenticides lower the carnivore’s immune systems.

Question 22

Explain the case study of pneumonia in bighorn sheep. What are the impacts to bighorn sheep populations? How can domestic and wild sheep populations be managed to reduce the threat of pneumonia in bighorn sheep populations?

Answer 22

Pneumonia: infectious disease that inflames the lungs and can lead to death; bacteria can be transmitted between species.

Bighorn sheep are highly susceptible to dying from this.
Female bighorns spread within the population and males spread between populations.
Reduce spillover from domestic sheep to wild bighorn sheep by vaccinations, fencing, reducing density, and grazing allotments.
Increase individual resistance within wild populations by improving nutrition and increasing genetic diversity.

Question 23

What is white-nose syndrome? When are bats typically exposed? What are the impacts of WNS to bat populations?

Answer 23

White-nose syndrome (WNS): a relatively recent infectious disease of hibernating bats in North America caused by the fungal pathogen Pseudogymnoascus destructans (Pd).

Estimated to have killed 5-6M bats in North America. Typically exposed during hibernation.