Lice

Lice are small, wingless insects that infest the skin and hair of their hosts, causing irritation and potential disease transmission. This chapter covers the biology, types, and management of lice infestations.

Biology and Environmental Preferences

Lice are obligate ectoparasites belonging to the order Phthiraptera. They are species-specific and are categorized into two main types based on their feeding behavior: biting (chewing) lice and sucking lice. Lice infestations, known as pediculosis, can cause significant discomfort, health issues, and economic losses in both animals and humans. This section will explore the biology of lice, their life cycles, clinical signs of infestations, diagnostic methods, and control and prevention strategies.

Life cycle

Lice have a simple life cycle consisting of eggs (nits), nymphs, and adults. They thrive in close, warm environments and are spread through direct contact. Animals are usually infected in autumn with significant infestation occurring over winter. Adult lice are seen easily with the naked eye and approximately the same size as a sesame seed.

1. Egg (Nit) Stage:
   • Nits are cemented to the hair or feathers of the host.
   • Eggs hatch in about 1-2 weeks.
2. Nymph Stage:
   • Nymphs resemble smaller versions of adults.
   • They undergo three molts over 2-3 weeks to reach the adult stage.
3. Adult Stage:
   • Adults live for about 30 days, during which they mate and lay eggs.
   • Entire life cycle occurs on the host.

Types of Lice

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. CAPCvet is a great resource to learn more!

Clinical signs and pathogenesis

Lice infestations can lead to various clinical signs and complications, primarily due to the lice’s feeding behavior and the host’s immune response.

1. Pruritus (Itching):
   • Caused by lice feeding and movement on the skin.
   • This leads to scratching, biting, and rubbing behaviors.
2. Alopecia (Hair Loss):
   • Resulting from excessive grooming or self-trauma.
3. Dermatitis:
   • Skin becomes red, inflamed, and scabby.
   • Secondary bacterial infections may occur due to skin damage.
4. Anemia:
   • Seen in severe infestations of sucking lice, particularly in young or debilitated animals.
5. Restlessness and Irritability:
   • Infested animals or humans may exhibit signs of discomfort and agitation.

Diagnosis

1. Visual Inspection:
   • Observing lice or nits on the hair, feathers, or skin.
   • Common sites: neck, shoulders, flanks, and around ears.
2. Microscopic Examination:
   • Confirming the presence and species of lice through microscopic analysis.
   • Identification of nits, nymphs, and adults.
3. Clinical Signs:
   • Correlating observed symptoms with lice infestations.

Summary

Lice infestations can cause significant discomfort and health issues in a variety of hosts. Understanding the life cycles and clinical signs of different types of lice, coupled with accurate diagnostic methods and integrated control measures, is essential for managing and preventing lice infestations. By implementing effective treatments and maintaining good environmental hygiene, infestations can be controlled, ensuring the well-being and health of animals and humans.

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