27 Internal Parasites.pdf

Chapter 27

Internal Parasites

Introduction

Larry R. McDougald

Trematodes, acanthocephalans, cestodes, and nematodes are im-

portant parasites ofpoultry. In many locales the modern tecMOJ-

ogy of rearing poultry has dramatically changed the importance

of many species. Parasites with complicated life cycles, involv-

ing intermediate hosts such as insects or snails, were virtually

eliminated when commercial poultry were brought inside. Today,

only a handful of these parasites are important in commercial

poultry, although many are found in small flocks reared in natu-

ral environments. A rich fauna ofinternal parasites can be found

by examination of birds from backyard flocks, feral, or free-

range birds. Wild birds of nonpoultry species have an abundant

fauna ofwonns ofall types. Many are important in the commer-

cial production of game birds. A few nematodes, such as the as-

carids, cecal worms, and capillarids, have direct life cycles and

are fecund enough to prosper in the poultry house envirorunent,

particularly where management does not require frequent

c1eanouts. Some cestodes are important, even though they use an

intermediate host, because the host also prospers in the poultry

house envirorunent.

Control of these parasites is difficult but important. Even

though there have been no new products registered specifically

for control of worms in chickens in recent years, excellent prod-

ucts approved for use in other animals can be used off-label by

veterinary prescription. Even though mild infections of the

worms cause little damage, some bring in other diseases, such as

the well-known relationship of Heterakis gallinarum with Histo-

monas meleagridis. Recent widespread clinical outbreaks of

blackhead disease (histomoniasis) underscore the need for ad-

vances in this area. Cestode infestations tend to build up when

beetle control is lax, signaling a need for better overall manage-

ment. Among anthelminthics, few have been approved for use in

poultry. Recent changes in the FDA's regulation of off-label use

of products by veterinarians provide some relief by allowing

poultry producers to take advantage of modem products.

Nematodes and Acanthocephalans

Thomas A. Yazwinski and Christopher A. Tucker

Introduction

Nematodes constitute the most important group ofhelminth par-

asites ofpoultry in the number ofspecies, the number of animals

infected, and the amOlUlt of damage done. The trematodes, ces-

todes, and acanthocephalans are of relatively minor importance

in commercial poultry, but are important in other birds.

This chapter is designed to aid the diagnostician in identifying

predominant nematodes of poultry throughout the world. Those

reported in chickens raised in the United States are listed in Table

27.1; those from other domestic poultry and/or commercially

raised game birds from the United States are listed in Table 27.2.

(Nematodes from areas other than North America are mentioned

in the text but are not listed in the tables.) Avian nematodes often

have a broad host range. Accordingly, nematodes found in wild

birds may constitute a hazard for commercially raised birds (see

Table 27.3). For a more detailed description ofindividual species,

see the references listed in the previous editions ofthis book (62,

80) or other reviews (I, 12, 14, 16, 47). A checklist and descrip-

tions are available for parasites reported from the bobwhite quail

and waterfowl (43, 48). Additionally, the internal and external

parasites of ratites are thoroughly discussed by Craig and

Diamond in Ratite Management, Medicine and Surgery (73).

The genus and species names used in this chapter are those of

Yamaguti (83), except where usage by recognized authorities su-

persedes his classification. Yamaguti described 25 families ofne~

matodes from 9 orders in avian species; 13 of these families

(Strongyloididae, Trichuridae, Syngamidae, Trichostrongylidae,

Subuluridae, Heterakidae, Ascarididae, Spiruridae, Thelaziidae,

Gnathostomatidae, Physalopteridea, Acuariidae, and Dipetalone-

matidae) contain species that infect poultry. Levine (46) used a

We thank ~ious authors of this chapter, Robert Norton and Michael Ruff,

as well as previous authors, for their contributions to earlier versions of this

.",k.

1025

Table 27.1. Nematodes reported from chickens in the United States.

Nematode

Locatlon

Intermediate Host

Other DefInitive Host

Baylisascans procyonis

Brain

Raccoons (accidental parasite in chicken, turkey,

partridge, quail)

Turkey, duck, grouse, guinea fOwl, peafowl, pigeon,

quail

Turkey, goose, guinea fOwl, pheasant, peafowl, quall

Turkey, duck, guinea fowl, partridge, pheasant, quall

Turkey, goose, grouse, guinea foWl, partridge,

pheasant, quail

Turkey, partridge, pheasant, quall

Oxyspirura mansoni

Eye

Cockroach

Syngamus trachea

Gapj/larJa contorts

C.8nnulata

Trachea

Mouth, esophagus, crop

Esophagus, crop

None

None or earthworm

Earthworm

Gongylonema ingluvicola Crop, esophagus,

Beetle, cockroach

proventriculus

Dispharynx nasuta

Proventriculus

Sowbug

Turkey, grouse, guinea fowl, partridge, pheasant,

pigeon, quail

Turkey, duck, grouse, pigeon, quail

Turkey, duck, goose, guinea fowl, pigeon, quail

Tetrameres americana

Proventriculus

Grasshopper, cockroach

T.fiss;sp;na

Proventriculus

Amphipod, grasshopper,

cockroach, earthworm

Cheilospirua hamulosa

Gizzard

Grasshopper, beetle

Turkey, grouse, guinea fowl, pheasant, quail

Turkey, duck, goose, quail

Turkey, duck, goose, partridge, pheasant

Ascaridia gal/i

Small intestine

None

Gapfflaria anatls

Small intestine,

None

cecum, cloaca

C. bursata

Small intestine

Earthworm

Turkey, goose, pheasant

Turkey, duck, goose, grouse, guinea fowl, partridge,

pheasant, pigeon, quail

Turkey, goose, guinea fowl, cecum pigeon, quail

Turkey, duck, goose, grouse, guinea fowl, partridge,

pheasant, qUail

Turkey, dove, duck, grouse, guinea fowl, partridge,

pheasant, quail

Guinea fowl, quail

C. caucJinflata

Small intestine

Earthworm

capillaria obsignata

Small intestine

None

Heterakis gaflinarum

None

Subu/ura brumpti

eec,m

Earwig, grasshopper,

beetle, cockroach

S. strongy//na

Cecum

Beetle, cockroach,

grasshopper

Strongyfoides Bvium

Cecum

None

Turkey, goose, grouse, quail

Turkey, duck, goose, guinea fowl, pigElOll, quail

Trichostrongyfus tenuis

Cecum

None

Table 27.2. Nematodes reported from poultry or commercially raised game birds other than chickens.

Nom"'"

Location

Intermediate Host

Other DefinitiVe Host

Cyathostoma bronchia/is

Cymea colin/

Tetrameres cram!

Microtetrameres helix

AmIdostomum anseris

A. skljablni

Ascaridia coIumbae

A. dissim/fis

A. num/dee

Omlthostrongyfus quadriradiatus

Heterakis dlspar

H. isotonche

Cspillaria columbae

Trachea

Proventriculus

Gizzard

Small intestine

Cecum

Large intestine

None or earthworm

Cockroach

Amphipod

Grasshopper

None

Turkey, duck, goose. (chicken)

l1Jrkey, grouse, prairie chicken, quall, (chlcken)-

Duck

Pigeon

Duck, goose, pigeon

Duck, pigeon, (chicken)

Pigeon, dove

Turkey

Guinea fowl

Pigeon, dove

Duck, goose

Duck, grouse, pheasant, prairie chicken, quail

Pigeon, dove

• Experimental

1026

eec,m

CHAPTER 27 Internal Parasites. 1027

Teble 27.3. Nematodes reported from wild birds in the United States that pose a potential problem for pouhry or commercially raised

game birds.

Location

Intermediate Host

Definitive Host

Oxyspirura petrowi

Splendldofilaria californiensis

Singhfil8lia hayesi

SpJendidofilaria pectoralis

Chand/erel/a chftwoodae

AproctelJa stoddardl

Cardlofilsrla nf/esi

Echinuta uncinata

Ey.

Heert

Subcutaneous

Connective tissues

Body cavity

Esophagus, gizzard,

proventriculus,

small intestine

Proventriculus, gizzard

Proventriculus

Proventriculus, gizzard

Proventriculus

Gizzard

Gizza'"

Small intestine

Small intestine, cecum

Small intestine

cecum, large intestine

cecum

Unknown

Mosquito

Water flea

Grouse, qUail, pheasant, prairie chicken

Quail

Turkey. quail

Grouse

Turkey, dove, quail

Chicken

Duck, goose

E. paNa

Tettameres pattersoni

T. ryjikovl

Cymea neelJ

C. pileata

Physaloptera acuticauda

Amidostomum acutum

A. raillietl

Chellospirura spinosa

Cymea euryceJW

Epomidlostornum uncinatum

Streptocata crassicauda

Ascsrldla bonasae

A. compar

Porrocaecum ensicaudatum

Capillaria phasianina

C. trielens

Aulonocephalus lindquisti

A pennula

A qusrlcensis

Unknown

Grasshopper, cockroach

Unknown

None

Grasshopper

Unknown

None

Amphipod

None

Earthworm

Unknown

Duck, goose

Quail

Duck

Turkey

Quail

Chicken, pheasant

Duck

Duck, dove

Grouse, partridge, pheasant, qUail, turkey

Pheasant, quail, turkey

Chicken, duck, goose, pigeon

Chicken, duck

Grouse

Grouse, partridge, pheasant, quail

Chicken, duck

Partridge, pheasant, guinea fowl

Turkey

Quail

Turkey

Quail

Note: Some of these have been reported from domestic poultry outside of the United States.

similar classification but substituted Onchocercidae for Dipeta-

lonematidae. The classification used for families in this chapter

is that given in the CIH keys in a series on the nematode parasite

ofvertebrates edited by Anderson and Bain (3).

diately anterior to the esophagus (Fig. 27.24A). The mouth cav-

ity may be reduced or absent in some groups of nematodes. The

esophagus may be simple (consisting of 1 undivided part) or

more complex (consisting of a short anterior muscular part and a

long posterior glandular part). A bulb may or may not be present

at the posterior end (Fig. 27.20). The intestine follows the esoph-

agus and leads to a short rectum connecting to the anal or cloa-

cal opening in the posterior.

Nematodes are usually sexually distinct. Sexual dimorphism is

remarkably demonstrated by some species ofnematodes, such as

Tetrameres americana (Fig. 27.7), in which the elongate male

worm is much smaller than the globule-shaped female. The nem-

atode male usually can be distinguished from the female by the

presence of 2 (rarely I) chitinous structures known as spicules,

located in the posterior end ofthe body. The spicules (Fig. 27.20)

have been considered as organs for use during copulation, keep-

ing the vulva and vagina open and, to some extent, guiding the

amoeboid sperm into the female reproductive tract. Eggs or lar-

vae are discharged through the vulva, the position ofwhich varies

considerably between genera ofnematodes.

General Morphology of the Nematodes

Used in Identification

Nematodes, or roundworms, are usually spindle shaped with the

anterior and posterior ends attenuated. The body covering, or cu-

ticle, is often marked by transverse grooves. Longitudinal folds,

or alae, may be present at the anterior (cervical alae) or posterior

(caudal alae, Fig. 27.14) part ofthe body. The latter are found on

the tail of the male worm, and in the case of certain groups, are

modified to form a bursa (see Fig. 27.18B). Cuticular ornamen-

tations occasionally found on the anterior extremities take the

form of spines, cordons, or shields (see Fig. 27.6A).

The mouth opening, located at the anterior end ofthe body, is

usually surrounded by lips bearing sensory organs (Fig. 27.5A).

In some nematodes, the mouth leads directly into a cavity inune-

1028 • SECTION rv Parasitic Diseases

Nematode Development

Species of nematodes in poultry have either a direct or an indi-

reet life cycle; about one-half of the species require no inverte-

brate intermediate hosts, whereas the others depend on such in-

tennediate hosts as insects, snails, and slugs. Several use

paratenic hosts which facilitate parasite survival and dispersal

between hosts.

Nematodes normally pass through four developmental stages

and four sucessive molting events (shedding of the cuticle) be-

fore adulthood.

Eggs laid by the female nematode reach the outside in the

droppings, regardless of the location of the adult wonns. Some

eggs are embryonated before leaving the host, but most require

suitable environmental conditions outside the host for embryona-

tion and the development of infective larvae. Most eggs hatch

only when consumed by a new host, but a few hatch in the envi-

ronment and release free-living larvae. Eggs become embry-

onated within a few days to several weeks. For nematodes with

direct life cycles, the definitive host becomes infected by eating

free, infective larvae or embryonated eggs containing the second-

stage larvae. For those with indirect life cycles, the intennediate

host ingests the embryonated eggs or free larvae. The definitive

host becomes infected either by eating the infected intermediate

host or by injection of infective larvae by a blood-feeding arthr0-

pod. Direct life cycles predominate among nematodes affecting

conunercial poultry in the United States.

Nematodes

Nematodes of the Upper Digestive

Tract

Capillaria annulata Molin 1858, capillariidae

Hosts

C. annuJata has been reported in chicken, turkey, goose, grouse,

guinea fowl, partridge, pheasant, and quail. It is found in the mu·

cosa ofthe esophagus and the crop.

.... \

Morphology

C. annuJata are long, slender wonns, similar in appearance to C.

contorta but easily differentiated by a cuticular swelling at the

back ofthe head (Fig. 27.1A). The male is usually 10-26 nun long

and S2-741Jm wide; the tail ends in 2 inconspicuous round lateraJ

flaps, united dorsally by a cuticular flap; the spicule sheath is

beset with fine spines (Fig. 27.1B); and the spicule is 1.12-11.63

rom long. The female is usually 25--60 rom long and 77-120 IJlll

wide; the posterior portion of the body (posterior to vulva) is

about 7 times as long as the anterior portion; the circular vulva is

located opposite the tennination of the esophagus; and the eggs

are operculated (Fig. 27.1C) and are 55--66 X 26-28 f.UJl.

Life Cycle

Eggs pass out in the droppings of infected birds and require 24

days or more to develop. Two species of earthworms, Eisenia

foetidus and AJioJobophoro caliginosus, serve as intermediate

hosts of the crop wonn (78).

27.1. Capillaria annulata. A. Head end. B. Male tall. (After Clurea)

C. Egg.

Pathogenicity

The crop mucosa is thickened with enlargement of the glands,

and there is inflammation of the crop and esophageal walls. In

heavy infections, the inner surface of the crop becomes rough-

ened and badly macerated. Masses of wonns concentrate in the

sloughing tissue.

This wonn has been associated with the death of turkeys,

pheasants, quail, and other gallinaceous game birds. Other signs

include malnutrition, emaciation, and severe anemia.

Capillaria contorta Creplin 1839, Capillariidae

Hosts

C. contorta has been reported in chicken, turkey, duck, guinea

fowl, partridge, pheasant, pigeons and quail. It is found in the

mucosa ofthe esophagus, the crop, and sometimes the mouth.

...

.. :

CHAPTER 27 Internal Parasites. 1029

'Z7.3. Echinura uncinatB. A. Head. B. Male tail. (After Aomanova)

27..2. Capillaria contorta. A. Region of vulva. (After Eberth) B. Male

tail. (After Travassos)

Echinura uncinata (Rudolphi 1819) So/ovlev

1912, Acuariidae

Hosts

E. uncinata has been reported in wild and domestic ducks and

geese and in wild and domestic birds in Canada.

Morphology

C. contorta has a threadlike body, attenuated anteriorly and paS·

teriorly; its head is without a cuticular swelling. The male is 8-17

nun long and 60-70 flIll wide; there are 2 tenninallaterodorsal

prominences on the tail end; the spicule is very slender and trans-

parent, about 800 flIlllong; and the spicule sheath is covered with

fine hairlike processes (Fig. 27.2B). The female is 15-60 nun

long and 120-150 }JIll wide; and the vulva is prominent, circular,

and situated near the beginning of the intestine (Fig. 27.2A).

Location

E. uncinata may be found in the mucosa of the esophagus,

proventriculus, gizzard, and small intestine. There is a report of

this parasite in air sacs.

Morphology

E. uncinata is similar to Cheilospirura and Dispharynx; however,

the cordons are not recurrent and anastomose posteriorly (Fig.

27.3A). The male is 8-10 nun long and 300--500 ~ wide; the

left spicule is 700--900 IlIlllong; and the right spicule is 350 }JIll

long (Fig. 27.3B). The female is 12-18.5 mm long and 515 J.Ull

wide; the tail is 250 ~m long; the vulva is 1.0-1.4 nun from the

end ofthe tail; the eggs are 28-37 X 17-23 J.I.IIl and embryonated

when laid.

Life Cycle

Eggs are deposited in tunnels in the crop mucosa and escape into

the Iwnen of the crop and esophagus with the sloughed mucosa.

They are abundant in droppings from infected birds. Approxi-

mately 1 month is required for embryonation. The life cycle is di-

rect, and infection is initiated with the ingestion of embryonated

eggs. Worms mature 1-2 months after infection.

Life Cycle

E.uncinata utilizes water fleas of the genus Daphnia as an inter·

mediate host. Eggs are ingested by water fleas and release the lar-

vae, which become infective after 12-14 days. Adults mature 51

days after ingestion of water fleas by chickens or other hosts.

Pathogenicity

In light infections the wall of the crop and esophagus becomes

slightly thickened and inflamed. In heavy infections, a flocculent

exudate covers a mucosa that is inflamed, thickened, and slough-

ing. The crop may become nonfunctional. In heavy infections,

the woems may invade the mouth and upper esophagus.

Infected birds become droopy, weak, and emaciated. Deaths

have been observed among infected wild turkeys, Hungarian par·

tridges, and quail in the United States.

Pathogenicity

Onset of mortality may be rapid, without any previous signs.

Nodules may form in the proventriculus; however, in chronic in·

feetions, these may contain only inspissated pus. Birds may be

emaciated and listless.

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