#3 Arthropods and Wildlife Health pt 1

Do parasites/pathogens usually cause only a single problem?

No, arthropods often cause multiple, overlapping problems

• (e.g., annoyance, blood loss, dermatitis, toxicosis, disease transmission)

What are the main ways arthropods directly cause disease in hosts? (first 3)

• Annoyance

• Blood loss

• Myiasis (maggot infestation)

What are the main ways arthropods directly cause disease in hosts? (last 3)

• Dermatitis (skin inflammation)

• Direct toxicosis (venom or toxin injection)

• Transmission of other parasites (vectors)

How does annoyance from arthropods affect hosts?

Annoyance creates

• energetic costs

• alters behavior

• reduces feeding time

• may decrease survival and reproduction

How do biting flies affect cattle?

• Weight loss

• Reduced reproduction

• Reduced milk yield

How do insects affect reindeer and caribou?

• Spend more time avoiding insects (snowfields, windy ridges, water)

• Feed less

• Lose body weight

• Have lower birth rates and recruitment

• May run wildly to escape flies

What are examples of arthropods that cause blood loss?

• Winter ticks (Dermacentor albipictus)

• Swallow bugs (Oeciacus vicarius)

• Blood-sucking maggots (Protocalliphora spp.)

• Mosquitoes

Myiasis

Invasion of living tissue by fly larvae (maggots)

What are the three types of myiasis?

1. Accidental

2. Facultative

3. Obligate

Accidental myiasis

Larvae do not require a host but accidentally infect one (e.g., fly lays eggs in a sleeping person’s nose)

Facultative myiasis

Larvae normally develop on carrion but may invade wounds or soiled tissue.

• Common in blow flies

Obligate myiasis

Larvae must develop in living tissue

What is an example of obligate myiasis?

• New World screwworm (Cochliomyia hominivorax)

• Cuterebra spp. (rodent botflies)

• Deer head bots (Cephenemyia spp.)

• Dermatobia hominis

What happened with screwworm in North America?

It was eradicated using sterile male releases but re-emerged in 2016 in Florida Keys, killing endangered Key deer

Deer head bots cause what type of myiasis?

Obligate myiasis

Direct toxicosis

Disease caused by toxins injected by arthropods

Tick paralysis

Ascending flaccid paralysis caused by neurotoxins in tick saliva.

• Removal of the tick usually resolves symptoms

Which arthropods can cause envenomization? (first 3)

• Spiders

• Scorpions

• Bees

Which arthropods can cause envenomization? (last 3)

• Wasps

• Fire ants

• Some ticks

Dermatitis

Inflammation of the skin caused by parasites or allergic reactions

What are signs of hypersensitivity dermatitis?

• Hair loss

• Thickened skin

• Intense itching

• Secondary bacterial infections

What characteristics increase vector transmission?

• Feeding on multiple hosts

• Repeated feeding

• Strong dispersal ability

• Broad host range (generalists)

Why are 3-host ticks more likely to transmit pathogens?

They feed on different hosts at each life stage, increasing transmission opportunities

What is a mechanical vector?

Transmits pathogens without development or multiplication of the pathogen inside the vector.

• Example:

  • Tularemia

  • Avian pox

  • Enteric bacteria

Biological vector

A vector in which the pathogen undergoes development and/or multiplication within the vector

What are the three types of biological transmission?

• Developmental (cyclodevelopmental)

• Propagative

• Cyclopropagative

Developmental transmission

Pathogen undergoes obligate development in the vector (no multiplication)

Propagative transmission

Pathogen multiplies in the vector but does not change form

Cyclopropagative transmission

Pathogen both develops and multiplies in the vector

What determines ecological maintenance of vector-borne diseases? (first 3)

• Geographic overlap of host, vector, pathogen

• Vector competence

• Feeding preferences

What determines ecological maintenance of vector-borne diseases? (last 3)

• Host availability

• Seasonality

• Vector abundance