External Parasites

Part of Veterinary Medicine

Identifying and controlling ticks, mites, lice, flies, and other external parasites that damage livestock health and productivity.

Why This Matters

External parasites are among the most visible and persistent threats to livestock health. Ticks transmit lethal blood parasites. Mange mites destroy skin condition and drive animals to exhaustion through constant irritation. Lice reduce growth rates and milk production through blood loss and behavioral disturbance. Flies spread disease, cause myiasis (maggot infestation of wounds), and reduce productivity through harassment that prevents animals from resting and grazing normally.

In a post-collapse environment, the loss of commercial acaricides (tick-killers) and insecticides does not mean the loss of all control options. Many effective traditional treatments for external parasites were in use before synthetic chemicals existed, and these botanical and physical methods can be revived. Understanding which parasites you are dealing with, their life cycles, and their vulnerabilities allows rational control even with limited inputs.

External parasite control also has direct human health implications. Several tick species transmit diseases to humans, flies spread pathogens between animals and food, and mange mites can transfer from animals to humans. Controlling parasites on your livestock protects the people working with them.

Ticks

Ticks are obligate blood feeders that transmit a range of serious diseases including anaplasmosis, babesiosis (redwater fever), theileriosis, ehrlichiosis, and heartwater — most of which cause high mortality in naive animals. Tick species are highly regional; knowing the dominant tick species in your area determines which diseases to expect and which control methods are most effective.

Identification: Hard ticks (Ixodidae) have a hard scutum plate on the back. Common livestock ticks worldwide include Boophilus (one-host, cattle, tropical), Amblyomma (three-host, cattle and sheep, tropical and subtropical), Rhipicephalus, and Ixodes (temperate, Lyme disease vector).

Life cycle: Most ticks have three stages — larva, nymph, adult — each requiring a blood meal. One-host ticks complete all stages on a single animal. Three-host ticks feed on potentially different animals at each stage, falling off between feeds to molt in the environment. Understanding this determines where control is most effective: one-host ticks are controlled entirely on the animal, while three-host tick control also requires managing tick habitat.

Physical control methods:

• Hand-picking: Time-intensive but effective for small flocks. Use tweezers or dedicated tick removers — grasp as close to the skin as possible and pull straight out. Avoid twisting or squeezing the body (forces pathogens into the bite site). Drop ticks into oil, alcohol, or fire.
• Grooming with brushes: Disrupts attached ticks and removes feeding larvae. Daily grooming significantly reduces tick load.
• Burn and clear tick habitat: Ticks in temperate zones accumulate in long grass, woodland edges, and leaf litter. Clear and burn these areas near livestock housing.

Botanical acaricides:

• Neem oil (Azadirachta indica): Diluted neem oil (2–5% in water with a small amount of soap as emulsifier) applied to the skin is an effective tick repellent and kills newly attached ticks. Apply by spraying or sponging every 5–7 days during peak tick season.
• Derris/rotenone: Ground root of Derris species, historically used as both insecticide and fish poison. Apply as dust or aqueous extract to animal skin. Toxic to fish — do not wash treated animals into streams.
• Tobacco infusion: Tobacco leaves steeped in water for 24 hours, strained and diluted, used as a wash. Nicotine is toxic to ticks. Effective as a topical treatment; do not use on animals that may groom the treated area aggressively.

Mange Mites

Mange is caused by microscopic mites that either burrow into the skin (sarcoptic mange, demodectic mange) or live on the skin surface (psoroptic mange, chorioptic mange). All cause intense itching, hair loss, skin thickening, and secondary bacterial infection if untreated.

Sarcoptic mange: Burrowing mites. Affects all species. Intensely pruritic — affected animals rub constantly against objects, developing raw, thickened, crusty skin. Spreads rapidly between animals in close contact. Also transmits to humans (causes “scabies”).

Psoroptic mange (sheep scab): Surface-feeding mites causing severe fleece loss and dermatitis in sheep. Historically devastated sheep flocks in pre-antiparasitic eras. Requires quarantine and systematic treatment.

Chorioptic mange: Leg and foot mites, common in feathered-leg horses and heavily fleeced breeds. Less severe than other types.

Treatment options:

• Sulfur: Powdered sulfur mixed with petroleum jelly or vegetable oil and rubbed into affected skin is a historical and effective mange treatment. Apply to all affected areas and surrounding skin every 5–7 days for 4–6 treatments. Sulfur kills mites by contact.
• Lime sulfur wash: Diluted hydrated lime mixed with sulfur, applied as a whole-body wash. Effective for sarcoptic and psoroptic mange.
• Isolation: Mange spreads through direct contact. Separate affected animals immediately; use separate handling equipment and wash hands after contact.

Lice

Lice are species-specific: cattle lice do not infest sheep, sheep lice do not infest cattle. All livestock species host their own louse species. Heavy infestations cause significant production losses through blood loss (sucking lice), irritation, and reduced feed efficiency.

Signs: Intense itching and rubbing, poor coat condition, visible lice and nits (eggs attached to hair shafts) on close inspection (part the hair at the neck, shoulder, and tail base where lice concentrate).

Seasonal pattern: Louse populations peak in winter, when animals are housed closely together and coat is longest. They decline naturally with spring warmth and shedding.

Control:

• Physical treatment: Fine-toothed combing removes lice and nits from small animals. Not practical for large herds.
• Dusting with pyrethrum powder: Pyrethrum (from Chrysanthemum cinerariifolium) is a botanical insecticide effective against lice. Apply to the coat by dusting or rubbing in powder, paying attention to the neck, back, and tail base. Repeat after 10–14 days to catch eggs that have hatched.
• Reduce crowding: Lice spread through contact. Reducing stocking density during housed periods reduces transmission rates.

Blowfly Strike and Myiasis

In warm, moist conditions, blowflies (Lucilia, Calliphora species) lay eggs in wounds, soiled fleece, or any damp area of skin. The larvae (maggots) hatch within hours and feed on living tissue, causing severe damage that can kill an animal within days if not treated.

Sheep with soiled fleece (from diarrhea, urine scald, or wounds) are particularly vulnerable. Animals in humid climates are at higher risk.

Treatment: Clip all fleece from the affected area, remove all maggots by hand and with salt water flushing, clean the wound thoroughly. Apply an antiseptic and repellent. Neem oil applied to cleaned wounds deters further egg-laying.

Prevention: Keep fleece trimmed around the tail and perineum (crutching). Treat diarrhea promptly. Inspect all animals daily during warm, humid weather.

Integrated Approach

No single treatment eliminates external parasites permanently. Effective control combines:

1. Reduction of parasite habitat — clear tick habitat, improve drainage, reduce manure accumulation
2. Regular inspection — detect infestations early when control is easier
3. Targeted treatment — treat affected animals with appropriate methods
4. Isolation of new animals — quarantine before introducing to the herd
5. Rotation of treatment methods — avoids development of resistance

Document what you observe and what works. Regional variation in parasite species, seasonality, and effective botanical treatments is significant. Knowledge built from local experience is the most durable resource.