Parasites

Introductory Recaps

• Parasitism occurs in varying degrees:

1. parasitiasis- here the parasite is present in or on the animal host, and is potentially pathogenic but the animal does not show any outward clinical signs of disease

Introductory Recaps cont.

• Parasitism occurs in varying degrees:

1. parasitosis- here the parasite is present in or on the body of the animal and does produce obvious injury or harm to the host manifesting in clinical signs of parasitism.

Parasites

Internal Parasites

• Internal parasites may be divided into four (4) classifications:

• Roundworms - (Nematodes)

• Tapeworms - (Cestodes)

• Flukes - (Trematodes)

• Protozoa - (Coccidia)

Roundworms - (Nematodes)

• The roundworms are by far the most economically important internal parasites of goats. Flukes produce damage of economic importance in some geographic areas, while adult tapeworms are usually of minor importance.

Roundworms - (Nematodes) • Large stomach worm, barber pole worm, twisted worm - Haemonchus

• Brown stomach worm - Ostertagia

• Stomach/intestinal hairworm, small stomach worm – Trichostrongylus

• Thread-necked worm - Nematodirus

• Hookworm - Bonostomum

• Nodular worm – Oesophagostomum

• Large-mouthed bowel worm – Chabertia

• Whipworm - Trichuris

• Large lungworm - Dictyocaulus filaria

• Cooperia

• Strongyloides

Large stomach worm, barber pole worm,

twisted worm - Haemonchus • Description: Internal parasite. Adults are

10 – 30 mm long. Males are shorter than females and have an even, reddish color and a bursa with an asymmetrical dorsal lobe and barbed spicules. Females are identified as barber’s pole worms because their white ovaries are wound around their red blood-filled intestine.

• Life Cycle: Eggs laid by adults in the abomasum are passed in the feces and hatch on the ground. On pasture they undergo a typical series of molts, becoming infective in about 4 – 6 days. Cattle or goats/sheep then ingest the larvae, beginning the infection. Fertile adults appear in approximately 28 days, but it is important to note that signs of the disease can appear sooner because larvae and immature adults, as well as fertile adults, suck blood.

LCHaemonch

us.mp4

Barbers Pole Worm.mp4

How Does FAMACHA Work ???

• Since primary impact of

H. contortus is anemia,

one can indirectly

measure parasite burden

(and need for treatment)

by measuring anemia

The FAMACHA© System

• Eye color chart with five color

categories

• Compare chart with color of

mucous membranes of sheep or

goat

• Classification into one of five

color categories:

• 1 – not anemic

• 5 -- severely anemic

Scoring Famacha

Scoring.mp4

Scientific classification

Kingdom: Animalia

Phylum:Nemathelminthes

Class:Nematoda

Order:Strongylida

Superfamily:Trichostrongylo

idea

Family: Trichostrongylidae

Genus:Haemonchus

Species:H. contortus

(soulsby,1982)

Size :70-85, 41-48

micrometer

LIFE CYCLE

Difficult to control because

Short, direct life cycle

Prolific egg producer(5,000 eggs a day)

Can go into “hypobiotic”(arrested) state during winter to survive.

Can survive on pasture for a long time.(Soulsby,1982)

PP 15 days

Pathogenicity and symptoms

The nematode piercing the abomasum causes a number of significant complications in the infected sheep that can lead to death. The infected animals can display severe

dehydration,

diarrhea,

unthrift appearance,

lethargy, depressed low energy behavior, rough hair coat and uncoordinated movements.

reduced growth and poor reproductive performance

anemia

Bottlejaw

Drugs A valuable, limited resource that must be managed properly

1) Benzimidazoles

Fenbendazole(5-7.5mg/kg

bwt), Albendazole(5-

10mg/kg bwt),

2) Nicotinics

Levamisole(7.5mg/kg bwt),

Morantel(10 mg/kg bwt),

3) Macrolides

Avermectins

Ivermectin (1mg/5kg bwt),

Doramectin (1mg/5kg bwt),

Moxidectin. (Newest drug

has “Persistent activity)

Control

Integrated Parasite Management (IPM)

Goal is not to create parasite-free animals. It is normal for sheep and goats to have parasites. Goal is to prevent clinical disease and production losses.

Fecal egg counts(Egg per gram)

Deworm when:

>1,000 epg in spring, summer

>2,000 epg in fall, winter

FAMACHA© and Selective Deworming

A system to assess Haemonchus contortis infection in sheep and goats and the need for deworming individual animals

• Named for its originator:

Dr. Francois “Faffa” MAlan CHArt

Brown stomach worm - Ostertagia

• Description: Internal parasite. Before the larval forms are ingested, their development in the environment may have been arrested by hypobiosis, a survival mechanism in which the preparasitic stages on-pasture "avoid" adverse summer and winter conditions. Ostertagia is one of the most economically significant parasites of cattle.

• Life Cycle: Adults in the abomasum lay eggs that pass in feces. Once hatched, larvae undergo two molds to become infective third-stage larvae which migrate onto herbage and are ingested by grazing cattle. Once ingested, these parasitic larvae grow and molt twice more to become egg-laying adults. The prepatent period is 18-25 days, though hypobiosis affects the process.

Stomach/intestinal hairworm, small stomach worm –

Trichostrongylus • Description: The adult worm is small (0.5 centimeter long) and hair like.

• Predilection sites: Stomach glands, small intestine.

• Geographic distribution: Widespread

• Life cycle: Trichostrongylus axei has a direct life cycle typical of nematodes. Larvae develop to infectivity on pasture in 4 to 6 days under optimal conditions of temperature and humidity.

• Significance: The stomach hairworm is important primarily in contributing to burdens of mixed worm species.

• Clinical effects on host: Trichostrongylus is usually part of a mixed infection, so its results are additive. The hairworm irritates and erodes the villi of the gut, damaging the capillaries and lymph vessels within these structures and causing blood loss into the gut. Parasite-induced trauma to the intestinal lining results in characteristic dark, foul-smelling diarrhea. Blood loss can cause anemia, edema, and rapid loss of condition.

• Diagnosis: Larvae can be identified by fecal culture – the small egg is not identifiable up to species as it may be confused with other strongyle eggs

Trichostrongylus spp.

• Morphology:

Zoonoses spp.

• T. axei

• T. orientalis

• T. probolorus

• T. skirjabini

• T. colubriformis

• ………………

Definitive host

Trichostrongylus colubriformis third-stage larva obtained after culture of faeces

from an artificially infected sheep.

Life cycle Prepatent period: 2-3 weeks

Trich. spicules

Nematodes - trichostrongylus.mp4

Thread-necked worm - Nematodirus

• Description: Internal parasite. Adults are up to 25 mm long.

• Life Cycle: Eggs develop slowly; the infective third stage is reached within the egg in 2 – 4 weeks and may remain within the egg for several months. Eggs are highly resistant, and those passed by calves in one season can infect calves the next. After ingestion of infective larvae, the adult stage is reached in approximately 3 weeks.

• Geographic Distribution: Worldwide.

• Significance: Heavy infections of Nematodirus can lead to decreased weight gain, particularly when other parasites are present. Larval stages are primarily responsible for harming the host animal. Large numbers of larvae can retard an animal’s growth and even cause destruction of the intestinal wall.

Nematodirus.

www.djoralaeknin.com.mp4

LCNematodirus and the

warning map - sheep

worming.mp4

• Anterior end is bent toward its

back. The mouth is cup-shaped

and has two cutting plates.

Males are 12-17 mm long;

females are 19-26 mm

• Can cause anemia, edema, and

general unthriftiness. Symptoms

are generally similar to those of

the stomach worm. Adult worms

attach to the intestinal wall and

suck blood. Bleeding often

continues even after the parasite

is gone.

Hookworm - Bonostomum

Nodular worm – Oesophagostomum

• Description: Internal parasite. Adult worms are stout bodied and 14 – 22 mm long.

• Life Cycle: Adults in the intestine lay eggs which are passed in feces. Larvae pass through a series of molts and reach the infective third stage in approximately 7 days. When ingested with herbage, the larvae penetrate the wall of the host animal’s intestine, forming nodules anywhere between the stomach and the rectum. After 5 – 7 days they return to the intestinal lumen and travel to the colon, where they undergo a final molt and mature into adults. Eggs appear in the feces about 41 days after the larvae are ingested.

• Geographic Distribution: Worldwide, particularly in wet, temperate climates.

• Significance: Infective larvae burrow into the intestinal wall, causing the formation of pea-sized nodules called granulomas. Granulomas impair intestinal function, particularly fluid absorption. The result is black, foul diarrhea which is very debilitating. The disease oesophagostomiasis is characterized by anemia and edema in addition to the explosive diarrhea. When worms are present in large numbers. Young stock in particular are affected seriously and can die.

Oesophagostomum - Video Learning -

WizScience.com.mp4

Oesophagostomum

Large-mouthed bowel worm – Chabertia • General Description: Nematodes with a large oral

opening. Males are 13 to 14mm long, females, 17 to 20mm.

• Life Cycle: Direct life cycle. Infection by ingestion of infective third stage larvae. Prepatent period is about 48 to 54 days.

• Location: Colon

• Geographical Distribution: Worldwide

• Significance: Chabertia is significant only in heavily infected sheep. Reduced wool growth is the major result.

• Effect on Host: Adults ingest plugs of the bowel wall; some bleeding may occur. The affected part of the intestine is mildly irritated. Anaemia may occur when severe infections exist. Replacement of tissue and blood lost to parasites limits the energy the host may otherwise use for wool growth. Occasional diarrhoea may be seen.

• Diagnostic Information: Strongyle-type eggs appear in faeces.

• Control: Treatment of infected sheep with a suitable anthelmintic.

Whipworm - Trichuris

• Description: Internal parasites. Long

roundworms; the anterior part is long and thin while the posterior is much thicker, giving the appearance of a whip. The male posterior is curved.

• Life Cycle: Infective larvae develop within eggs after at least 3 weeks on pasture. The eggs are resistant to cold temperatures and dry conditions, and can therefore remain infective for years. Cattle become infected by ingesting embryonated eggs. Adults develop in 1 – 3 months.

• Geographic Distribution: Widespread.

• Significance: The effects of whipworm infection have not been determined, as affected animals exhibit clinical signs only occasionally. Those that do, experience typical "parasite worry“ and do not feed or sleep well. Scratching may produce skin wounds or bruises, and the coat becomes rough. Infestations with biting lice are heaviest in winter when cattle hair coats are thick.

Large lungworm - Dictyocaulus filaria

• White with a dark line running the full length of the worm. Length of males are 3 to 8 cm and females range from 5 to 10 cm.

• Accumulation of adult worms and eggs can occur in the airways and cause obstruction. This can cause the lung tissue to collapse. Suffocation can then occur. Animals can show a symptoms by coughing and having difficulty breathing.

Cooperia

• Cooperia species are nematodes of the small intestine of ruminants. Species in domestic animals are usually 5-9mm long and males have a prominent bursa in relation to their size. Cooperia curticei is easily recognized on microscopic examination by its coiled appearance that has been described as like a "watch spring", as shown in the accompanying image of a female.

• Cooperia are generally considered to be mild pathogens. They contribute secondary effects to the primary pathogens Ostertagia and Haemonchus in parasitic gastroenteritis. However, Cooperia punctata, pectinata and suranabada are believed to be more pathogenic since they penetrate the mucosa during larval development causing changes similar to those of intestinal species of Trichostrongylus

Strongyloides • Strongyloides stercoralis is an unusual

"parasite" in that it has both free-living and parasitic life cycles. In the parasitic life cycle, female worms are found in the superficial tissues of the human small intestine; there are apparently no parasitic males. The female worms produce larvae parthenogenically (without fertilization), and the larvae are passed in the host's feces. The presence of nematode larvae in a fecal sample is characteristic of strongylodiasis. Once passed in the feces, some of the larvae develop into "free-living" larvae, while others develop into "parasitic" larvae. The "free-living" larvae will complete their development in the soil and mature into free-living males and females. The free-living males and females mate, produce more larvae, and (as above) some of these larvae will develop into "free-living" larvae, while other will develop into "parasitic larvae."

Ascaris

McMaster

• ScientifEQ - Faecal Egg Counts

Explained.mp4

Tapeworms

• Broad tapeworm - Moniezia expansa

• Fringed tapeworm - Thysanosoma

actinioides

• Hydatid cysts - Echinococcus granulosus

• Cysticercosis - Taenia ovis

• Taenia hydatigena

• Gid - Taenia multiceps

Broad tapeworm - Moniezia expansa

The life cycle of Moniezia expansa involves sheep as the definitive host and soil mites

as the intermediate host. The tapeworm's eggs are passed in the sheep's feces, and

mites are infected when they eat the eggs; the metacestode stage in the mite is called a

cysticercoid. Sheep are infected when then ingest infected mites. This species of

tapeworm is unusual in that each proglottid contains two sets of female reproductive

organs

Fringed tapeworm - Thysanosoma actinioides

• Definitive hosts: ruminants

• Site of infection: small intestine

Typical size: up to 30 cm long

•

Distribution: cosmopolitan

•

Intermediate hosts: cysticercoids

develop in psocid lice; these lice are

ingested along with vegetation

Hydatid cysts - Echinococcus granulosus

• The life cycle of Echinococcus granulosus includes dogs (and other canines) as the definitive host, and a variety of species of warm blooded vertebrates (sheep, cattle, goats, and humans) as the intermediate host. The adult worms are very small, usually consisting of only three proglottids (total length = 3-6 mm), and they live in the dog's small intestine. Eggs are liberated in the host's feces, and when these eggs are ingested by the intermediate host they hatch in the host's small intestine. The larvae in the eggs penetrate the gut wall and enter the circulatory system. The larvae can be distributed throughout the intermediate host's body (although most end up in the liver) and grow into a stage called a hydatid cyst.

Cysticercosis - Taenia ovis

Taenia hydatigena • The life cycle of the Taenia tapeworm

starts in the host’s intestine, the host being a dog or cat. The worm can be unbelievably long (up to 5 yards for Taenia hydatigena) and is made of segments. Each segment contains an independent set of organs with new segments being created at the neck and older segments dropping off the tail. As segments mature, the reproductive tract of the segment becomes more and more prominent until it consists of a bag of tapeworm eggs. These segments, called proglottids, are passed with the feces into the world where an unsuspecting intermediate host (mouse, rabbit, deer, goat etc.) swallows one while feeding.

Gid - Taenia multiceps

• The life cycle of this parasite involves warm blood vertebrates as both the intermediate and definitive hosts.

• Infections with cenuri can cause pathology in the intermediate host. Human infections (acquired by accidental ingestion of eggs) have been reported. The cenuri of T. multiceps (sometimes called Cenurus cerebralis) can infect the brains of sheep/goats, causing a disease referred to as "gid" or "staggers." These terms refer to the behavior of sheep/goats infected with this parasite.

Flukes - Trematodes

• Common liver fluke - Fasciola hepatica

Flukes - Trematodes • The common name of this parasite, the "sheep liver fluke," is somewhat

misleading since this parasite is found in animals other than sheep (including cattle and humans), and the parasite resides in the bile ducts inside the liver rather than the liver itself. This species is a common parasite of sheep and cattle and, therefore, relatively easy to obtain. Thus, in introductory biology or zoology courses, it is often used as "THE" example of a digenetic trematode. This species has been studied extensively by parasitologists, and probably more is known about this species of digenetic trematode than any other. The adult parasites reside in the intrahepatic bile ducts, produce eggs, and the eggs are passed in the host's feces. After passing through the first intermediate host (a snail), cercariae encyst on vegetation. The definitive host is infected when it eats the contaminated vegetation. The metacercaria excysts in the definitive host's small intestine, and the immature worm penetrates the small intestine and migrates through the abdominal cavity to the host's liver. The juvenile worm penetrates and migrates through the host's liver and finally ends up in the bile ducts (view a diagram of the life-cycle). The migration of the worms through the host's liver, and the presence of the worms in the bile ducts, are responsible for the pathology associated with fascioliasis.

Flukes - Trematodes

Protozoa - Coccidia

• Coccidia (coccidiosis) - Eimeria

• The diseases caused by these parasites

are referred to collectively as coccidiosis,

and they vary tremendously in

virulence. Some species cause diseases

that result in mild symptoms that might go

unnoticed (i.e., mild diarrhea) and

eventually disappear, while other species

cause highly virulent infections that are

rapidly fatal.

Protozoa - Coccidia

Protozoa - Coccidia

• A host is infected when it ingests oocysts that have been passed in the feces of another host. The oocyst excysts in the host's small intestine, and the sporozoites contained within the oocyst are liberated. The sporozoites penetrate the cells of the host's small intestine and reproduce asexually. Each generation of asexual reproduction produces multiple merozoites; the merozoites are liberated from the cell and infect new cells. It is this stage of the infection that can result in destruction of massive numbers of cells in the host's small intestine and, ultimately, lead to the host's death. Some of the merozoites that enter the host's cells transform into gametocytes. The gametocytes transform into gametes, the gametes fuse, and the resulting zygote begins to develop into an oocyst. The developing oocyst escapes from the host's cell, and it is passed in the host's feces. Typically, when the oocyst is passed in the feces, it is not infective because it does not contain sporozoites; this is an unsporulated oocyst. After several days (or weeks, depending on the species) outside of the host's body, the oocyst completes development and sporozoites are found within; this is a sporulated oocyst, and it is infective to the next host

Protozoa - Coccidia

A severe

coccidiosis infection

in a small animal

Treatment/Prevention • To stop intestinal worms from accumulating, do not use the same pastures

for kidding every year.

• Rotate pastures used for grazing every 3-6 months.

• If clean grazing such as stubble is available, goats should be given an effective broad spectrum de-wormer before they are moved on to it.

• If possible, all animals that are de-wormed should be held in a dry lot for at least 3 days. This is because most de-wormers do not kill the parasite eggs, just the adults worms. Waiting 3 days will help the animal eliminate most of the parasite eggs in the dry lot and not on pasture where other animals may ingest the eggs.

• Prevent the post-kidding rise in parasite egg production.

• Have a veterinarian perform a fecal egg count to check the effectiveness of any de-worming or parasite control programs. This should be done 10-14 days after de-worming. Use these fecal egg counts to determine whether goats need additional de-wormings.

• Avoid resistance problems by not using the same products year after year.

• Select for animals that are parasite-resistant. These are goats that have a natural resistance to internal parasites. These animals are often identified through the use of fecal egg counts.

• In colder climates where the animals are moved off of pasture for the winter, a dose can be given just before the move is made.

• A second time for de-worming occurs 1 month prior to the kidding season. De-worming does about 2-4 weeks before kidding and then moving them to a safe pasture, will prevent the rise in production of worm eggs after kidding. If the does are not moved after this dose, additional doses are required at 3 week intervals throughout the kidding season. The final dose should be given 2-4 weeks after the last kid is born.

• A de-wormer for kids at weaning should also be given. After the de-worming, the kids should be moved to a "safe" pasture.

• Breeding males are often de-wormed 1 month before the breeding season

De-worming Program for Internal Parasites

Products Used to Treat Internal Parasites:

*Ivomec Sheep Drench (Ivermectin)

*Tramisol or Levasole (Levamisole)

*Bovatec (Lasalocid Sodium)

*Rumensin (Monensin

*Corid (Amprolium)

*Dectomax (Doramectin)

*Valbazen (Albendazole)

*Panacur (Fenbendazole)

* Many of these products are not labeled for use in goats.

Their use in these cases is considered "extra-label."

External Parasites Common to Goats:

• Lice - Damalinia

• Mites - Chorioptes, Psoroptes, Sarcoptes, Demodex

• Flies - Lucilia, Calliphora, Chrysomya

• Ked - Melophagus ovinus

• Ticks

• Nasal bot - Oestrus ovis

Lice - Damalinia

Goat lice affect only goats. They may

survive on sheep for about 5 to 7 days,

but not propagate. Lice from cattle do

not affect goats.

Lice spend their whole life on the goat.

Individual adult lice survive for about a

month.

The spread of lice is by direct contact

between goats. Crowded conditions for

goats enable rapid spread. At

shows, spread can occur with shared

grooming equipment, stalls or trailers.

Lice - Damalinia

Mites - Chorioptes, Psoroptes,

Sarcoptes, Demodex

• Mites are barely visible to the naked eye. The unsegmented abdomen is joined to the cephalothorax with little or no indication of separation.

• The adults are found in a wide variety of locations and under a wide variety of environmental conditions. Usually, the eggs are deposited on the soil surface, in crevices, or in some instances, under the skin of the host that they infest. The larvae that hatches (six-legged) seeks a blood meal and molts to an eight-legged nymph. More feeding and molting result in adult mites.

Mites - Chorioptes, Psoroptes,

Sarcoptes, Demodex

Flies - Lucilia, Calliphora, Chrysomya

Flies - Lucilia,

• It is responsible for initiating over 90 per cent of all flystrikes. The adult fly is metallic green/bronze in colour. Unlike the native blowflies, Lucilia cuprina breeds mostly on living sheep. Females are attracted to the smell of fleecerot and lay about 250 eggs in clusters in damp fleece. Body length head:abdomen is 9mm.

Calliphora

• Calliphora stygia - the Eastern Golden Haired Blowfly - is a native brown blowfly that prefers cooler conditions. It occurs in largest numbers in spring and autumn, but may be found on sunny days in winter as well. It disappears during the heat of summer. Although this species mainly breeds in carcasses, it can be troublesome in spring - especially in does with kidding stain. Body length head:abdomen is 13mm.

Chrysomya

• Chrysomya rufifacies, the green hairy maggot blowfly, is a secondary blowfly species. This means it normally does not strike goats or blow carcasses until primary maggots, like Lucilia or Calliphora, are already feeding. The adult fly is metallic green but can be distinguished from Lucilia by the broad bands on its rounder abdomen and by its black forelegs. The larvae, or "hairy maggots" appear dark and have sharp spines over much of the body. These maggots repel - and will actively feed on - primary maggots in carcasses. By doing this they help control Lucilia and so can be regarded as beneficial flies. However, on goats, they can cause extensive damage not only to the skin but also to the underlying tissue of struck goats. By the time these larvae reach full size on goats the animal has been struck for more than a week - initially by Lucilia, but then by Chrysomya. The very similar, but smaller, Chrysomya varipes fulfils a similar role. C. rufifacies is 9mm from head to abdomen.

Flies - Lucilia, Calliphora, Chrysomya

Ked - Melophagus ovinus

• Description: flat, leathery, reddish-brown insect about ¼ inch long; resembles a large tick but has only six legs and is a wingless, bloodsucking fly; a noticeable piercing mouthpart projects forward from the head.

• Damage caused: blood loss from keds may cause anemia in young lambs and reduced rate of gain in older lambs; keds and their pupae in wool result in "dirty wool" classification; sheep’s immune response to keds reduces capillary flow in skin resulting in reduced quantity and quality of wool; punctures from feeding cause "cockle" and downgrades hide value.

• Method of dispersal or infestation: host-to-host contact facilitated by the sheep’s close herding behavior and at breeding and nursing; keds move in great numbers from shorn adults to lambs; some dispersal between herds is via human handlers and on shearing equipment.

• Seasonality: numbers are highest during cool weather, especially on previously uninfested sheep that have not yet developed a protective immune response to keds.

Ticks

• The Brown dog tick seldom attacks animals other than dogs. It is most likely found where dogs are kept in or around the house. The brown dog tick is not known to transmit diseases to humans but may transmit disease among dogs.

The American dog tick is

also a common pest of pets

and humans in Florida. Dogs

are the preferred host,

although the American dog

tick will feed on other

warmblooded animals. The

nymphal stages of the

American dog tick usually

only attack rodents.

Ticks • The female dog tick lays 4000-6500 eggs and

then dies. The eggs hatch into seed ticks in 36-57 days. The unfed larvae crawl in search of a host and can live 540 days without food. When a small rodent is found, the larvae attach and feed for approximately 5 days. The larvae then drop off the host and molt to the nymphal stage. The nymphs crawl about in search of a rodent host, attach to it, and engorge with blood in 3-11 days. Nymphs can live without food for up to 584 days.

• Adults crawl about in search of dogs or large animals for a blood meal. Adults can live for up to 2 years without food. American dog tick adults and many other species can be found along roads, paths, and trails, on grass, and on other low vegetation in a "waiting position." As an animal passes by the tick will grasp it firmly and soon start feeding on its host. The males remain on the host for an indefinite period of time alternately feeding and mating. The females feed, mate, become engorged, and then drop off to lay their eggs.

• The American dog tick requires from 3 months to 3 years to complete a life cycle It is typically an outdoor tick and is dependent on climatic and environmental conditions for its eggs to hatch.

One Host Tick

Two Host Tick

Nasal bot - Oestrus ovis

• Description: Adult flies are _ to 5/8 inch long, wide-bodied, mottled yellowish to gray-brown, and quite hairy; mouthparts are rudimentary. Larvae are grublike maggots that reach one to one and one-fourth inch in length.

• Domestic animals affected: sheep, goats.

• Damaged caused: extreme annoyance during larviposition; later, during larval development, a snotty and sometimes bloody nasal discharge, loss of appetite, vigorous head shaking, secondary infection of the sinuses; sometimes death.

• Development: complete metamorphosis: egg (hatches within female), larval stages, pupa, adult fly.

• Generational time: typically one year, but spring larviposition may result in a complete developmental cycle that produces adults within 10 to 12 weeks.

Nasal bot - Oestrus ovis

• Upon being deposited in the nostril of a sheep, the larva crawls onto the mucous membrane of the nasal passage, where it will remain for at least two weeks. Development of the 1st instar larva may be delayed, and individuals from the same larviposition may spend from 1 to 9 months in the 1st instar. This plays a role in the overwintering cycle.The pupal stage lasts 1-2 months depending upon temperature

Diagnosis of External Parasites

• Parasites or the signs associated with

infestations can be observed upon routine

examination of the animal.

Treatment/Prevention

• Most external parasites are controlled on a flock/herd wide basis. This means that when one animal is diagnosed with external parasites, a dip, dust, or spray is used to treat the problem that animal as well as the entire flock/herd. The following table outlines the common products and the treatments used to treat the external parasites

Active Ingredient Effective Against **Treatments

*Malathion Mites, lice, keds 0.5% spray; 4% dust

*Lime-sulfur Mites, lice, keds 2-5% dip

*Coumaphos Mites, lice, keds 0.05-0.3% spray or dip; 0.5%-1% dust

*Phosmet Mites, lice, keds 0.15-0.25% dip

*Methoxychlor Mites, lice, keds,

ticks 0.5% spray or dip; 5% dust

* These products are not labeled for use in sheep and goats. Their use in these animals is considered "extra-label."

References

• www.Infovets.com

• Texas 4-H Goat Guide

• Veterinary Clinical Parasitology 8th Edition