Module 10: Veterinary Ectoparasites

Module 10.5: Mites, Lice, and Fleas

Mites

Mites are divided into families based on where you find them within or on the integument (skin).  The 4 families of veterinary importance are Sarcoptidae, Psoroptidae, Cheyletidae, and Demodecidae.

Table 10.7: Mites of Veterinary Importance

Family

Location in host integument

Common Species

Sarcoptidae 
Burrow into the skin Sarcoptes scabiei
Psoroptidae
Reside on skin Octodectes cynotis
Cheyletidae
Reside on skin Cheyletiella spp.
Demodecidae
Reside in hair follicles Demodex spp.

Similar to ticks, these arachnids undergo  and have 4 pairs (8 legs). Different than adult ticks, the majority of mites are microscopic and difficult to see with the naked eye. Therefore, the microscopic evaluation of skin scrapings (or sometimes scotch tape preps) is the first diagnostic test we reach for with suspected mite infestation.

Mite identification table

Below is a table of the common mites of veterinary importance. We will discuss these mites in more detail in Agents of Disease; however, their salient morphological features are listed below and will help guide you through the identification of the mites in the laboratory exercises.

Table 10.8: Morphological Features of Common Mites

Species of Mite

Family of Mite

Location on host

Transmission

Host

Identifying characteristics

Sarcoptes scabiei (Itch mite)
Sarcoptidae Burrow into the epidermis Direct contact Dogs, pigs, cattle, horses, sheep, humans Globose in shape, 3rd and 4th pairs of legs are short
Octodectes cynotis (ear mites)
Psoroptidae Reside on the skin or within the ear Direct contact Cat and dog Males have two suckers ventrally, females have long hairs attached to 3rd and 4th pair of legs
Cheyletiella spp. (walking dander)
Cheyletidae Reside on skin Direct contact- species specific Cat, dog, rabbit, humans Large claws
Demodex spp.
Demodecidae On hair follicle Skin to skin contact- normal inhabitant Multiple forms on dog, cat, cow, pig, human Cigar-shaped, 8 legs toward the head
Images of common mite species
Common Mite Species

Knowledge check


Lice

Lice are and transmitted by direct contact between animals.  Animals are usually infected in autumn and with significant infestation occurring over winter.  The two suborders of lice are Mallophaga (chewing lice) and Anoplura (sucking). Adult lice are seen easily with the naked eye and approximately the same size as a sesame seed.

In this laboratory, it will not be as important to identify lice to the specific genus or species, but I do want you to be able to identify a chewing versus sucking louse. It is important to be able to distinguish between the two as prevention and control and clinical signs differ between the two major types.

Table 10.9: Chewing Versus Sucking Louse

Suborder

Identifying characteristics

Movement

Mallophaga (biting/chewing lice)
  • Wide mandible, chewing parts
  • 3mm long
  • Yellow bodies 
  • Not bloodsuckers
Rapid/fast
Anoplura (bloodsucking lice)
  • Pointed nose
  • Large, 3-5mm
  • Dark blue, depending on the amount of blood ingested
  • Large claws to grasp hair
Slow
The two suborders of lice: Mallophaga (chewing lice) and Anoplura (sucking lice)
The two suborders of lice: Mallophaga (chewing lice) and Anoplura (sucking lice)

Knowledge check


Fleas

Fleas are of the order Siphonaptera.  Depending on the species of flea these parasites prefer to live on the host (dog or cat) or live in a nest (prairie dog fleas).  The most common flea in small animals (dogs/cats) is Ctenocephalides felis. While these fleas prefer to feed on dogs and cats, they will feed opportunistically on humans in a pinch.

Compared to lice, these insects are similar in size to sucking lice (sesame seed) but are rapidly moving. Under the microscope, the legs get larger posteriorly, with powerful posterior legs that are used for jumping from host to host. Fleas also have a pronotal and genial (it looks like a mustache!) comb that entomologists use to help speciate.

In the laboratory, you will not be asked to speciate fleas, but you will be required to distinguish a flea from other ectoparasites microscopically.

Table 10.10: Flea Species

Flea Species

Identifying characteristics

Transmission

Species commonly infected

Ctenocephalides felis
– eggs: white, oval with rounded ends
– larvae: found in the environment are maggot-like
– pupae: white-colored
– adults: eyes are present,  comb located on the head with spines pointed horizontal, 6 legs
– flea dirt: reddish-black pellets of dried blood excreted by adult fleas
Contact with infected environment Dog, cat
Ctenocephalides felis
Ctenocephalides felis male and female

Disease Transmitted by Ctenocephalides felis flea

Fleas have been transmitting terrible diseases to both humans and animals for thousands of years (anyone remember the Black Plague?) Below is a list of some diseases transmitted by fleas in general.

Table 10.11: Disease Transmitted by Ctenocephalides felis flea

Disease

Species affected

Type of disease transmitted

Bartonella henselae
cats, humans bacteria
Dipylidium caninum
Dog, cat, humans tapeworm (vector)

Knowledge check


Key Takeaways

  • Lice, mites, ticks, and fleas are some of the most common ectoparasites of veterinary species
  • Mites and ticks as nymphs and adults have 8 legs, but 6 when they are larvae
  • Lice and fleas have 6 legs as adults
  • Adult ticks, fleas, and lice can be seen with the naked eye
  • Mites often require a microscope to be observed
You have now reached the end of Module 10. If you are enrolled in CVM 6925, please go to the Canvas page and take the quiz: “Module 10: Ectoparasites quiz.” There is an assignment that accompanies the in-person laboratory for this module.

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