2. Producers used to dread outbreaks of oocysts can infect other birds. See the box
bloody diarrhea. An outbreak of coccid- “Coccidial Multiplication” for further details
iosis left untreated, eventually runs its on coccidia’s complex life cycle.
course, and most of the flock will survive.
The birds that recover from coccidiosis A coccidial infection differs from bacterial and
gain immunity, but production may never viral infections because coccidia are “self-lim-
recover. If the infection is severe, the gut iting” and usually stop multiplying before kill-
remains scarred and impaired, and stunted ing the bird.
broilers do not catch up in weight gain.
Coccidiosis is usually a disease of young
birds, but birds can be infected at any time
if never before exposed. Coccidia popula-
tions take time to build to dangerous lev-
els, therefore outbreaks usually occur
when birds are between 3 and 8 weeks of
age. Coccidiosis goes hand-in-hand with
gut diseases, because it damages the gut
Related ATTRA Posture of sick birds. Photo by Lloyd Keck, DVM. and allows bacteria to enter and cause sec-
Publications ondary infections. Coccidia are “species-
Sustainable Poultry: The production system and the stocking specific”—coccidia that affect chickens do
Production Overview density have a significant impact on coccid- not affect other livestock, and vice versa
Pastured Poultry iosis. Low-density production systems allow (see Species-Specific Parasites box).
Nutrition a low level of exposure in which immunity
develops without making the birds sick and Transmission in the
damaging performance. Birds are then
protected. However, as the size of flocks Environment
increase, the numbers of coccidia also grow Chickens get coccidiosis by eating oocysts
and can pose a threat to the flock. that have been shed in the droppings of
infected chickens. Infected chickens shed
oocysts for several days or weeks. Oocysts
Life Cycle and Types of sporulate within two days under the proper
Coccidia conditions and become infective. Chick-
Knowing how coccidia develop helps to ens pick them up by pecking on the ground
understand and control the disease. Coc- or in litter used for bedding in the house.
cidiosis is caused in poultry by a one-celled Oocysts can also be spread by insects,
parasite of the genus Eimeria. The life dust, wild birds, and humans (from shoes
cycle of Eimeria takes about four to seven and equipment).
days to complete. It begins when active
“oocysts” are picked up by the bird and
swallowed. An “oocyst” is a capsule with
a thick wall protecting the parasites. They
“sporulate” or become infective if moisture,
temperature, and oxygen become conducive
to growth. After a bird eats the oocysts,
coccidia imbed in the intestinal lining and
multiply several times, damaging tissue.
Coccidia are parasites, so they get their
nutrients from the chicken host. The mul-
tiplications eventually stop, usually before Coccidia multiply in intestinal cells.
Photo by Joe Beasley, DVM, PhD.
causing death of the bird. The bird sheds
the parasite in its droppings. These new
Page 2 ATTRA Parasite Management for Natural and Organic Poultry: Coccidiosis
4. Oocysts can survive many weeks in Symptoms and Diagnosis
the soil outdoors—as long as 600 days.
Outward signs of coccidiosis in chickens
(Farr and Wehr, 1949) The optimum tem-
include droopiness and listlessness, loss
perature for sporulation is around 72°F. The
of appetite, loss of yellow color in shanks,
rate of sporulation is slower if temperatures
pale combs and wattles, ruffled, unthrifty
are much cooler or hotter. Oocysts
feathers, huddling or acting chilled, blood
are killed either by freezing or very
or mucus in the feces, diarrhea, dehydra-
high temperatures.
tion, and even death. Other signs include
Sporulation also requires oxygen and mois- poor feed digestion, poor weight gain, and
ture (at least 20 percent moisture in the poor feed efficiency. Some symptoms can
litter for optimal sporulation). If the lit- be confused with other diseases. For exam-
ter feels damp to the back of your hand, ple, necrotic enteritis is a gut disease that
it is damp enough for sporulation. Once also causes bloody diarrhea.
sporulated, the oocyst remains infective for
Producers in the past identified coccid-
months if protected from very hot, dry, or
iosis outbreaks as either severe-acute
freezing conditions.
or chronic, which was less severe but
O
ocysts are In very large poultry houses, oocysts do not more widespread.
killed either last long in the litter because of the action of
If concerned about coccidiosis, do a nec-
by freezing
ammonia released by decomposition of lit-
ropsy—put on plastic gloves and cut open
ter and manure and by the action of molds
or very high temper- the chicken. Look at the intestines and then
and bacteria. However, there are usually
atures. cut them open. If done soon after death,
so many oocysts that birds continue to pick
it may be possible to identify characteris-
them up and get sick.
tic lesions or sores in the gut. Coccidiosis
causes a thickening of the intestines, which
The type and location of lesions in
the gut indicates the species of
Eimeria.
• Eimeria acervulina affects the upper
part of the small intestine. You may
see small red spots and white bands
Chicks can pick up on it.
oocysts both indoors
and on pasture. • Eimeria maxima affects the entire
small intestine. The intestines look
watery, and in later stages have blood
and mucus. The intestine may look
thickened and ballooned with red
pinpoint lesions.
• Eimeria tenella affects the blind sacs
(ceca) of the gut. They may be filled
with blood and pus and turn into a
solid core.
Small intestines affected
by Eimeria maxima. The
middle sample is opened
to show white spots.
Photo by Lloyd Keck,
DVM.
Note the ballooning. Photo by Lloyd Keck, DVM.
Page 4 ATTRA Parasite Management for Natural and Organic Poultry: Coccidiosis
5. make them feel like a sausage. There may the size of the flocks grows, more problems
be light-colored spots on the surface of the are encountered and more management is
gut, and inside the gut, hemorrhages and required for natural immunity.
streaks. If you want to confirm a diag-
Immunity is especially important in turkeys,
nosis, you can send scrapings of the gut
layers, breeders, and slow-growing broilers
lining to a state diagnostic lab. The USDA’s
that are kept longer than fast-growing broil-
Animal and Plant Health Inspection
ers marketed at a younger age.
Service’s Web site (www.aphis.usda.gov/vs/
npip) lists diagnostic labs.
Small-Scale Poultry Production Systems
Management for Control
Small poultry producers often provide outdoor access with either a per-
Management has always been important to manent house and yard or portable houses. Small pens that are moved
coccidiosis control, especially before drugs daily are also used.
were available. Management focuses on
reducing the number of coccidia to keep These small growers usually brood chicks in a separate area before mov-
ing them to the outdoor facility for growout. However, some growers
infection at a minimum until immunity
brood chickens in the same house in which they are grown. See ATTRA’s
is established. Sustainable Poultry: Production Overview for more information on small
production systems.
Natural Immunity
A small-scale, low-density production sys-
tem can allow a low level of exposure to
coccidia, which permits the chick to develop
immunity without triggering the disease. House with yard.
However, birds may not pick up enough
parasites to cause immunity, or they may
be overwhelmed by too many. In addition,
immunity is only species-specific. Expo-
sure to one type of coccidia will not protect
a chicken from the other six types that can
infect it.
Ea rly detect ion i s a ma na gement
method to avoid the use of preventative
medication. If you can catch the disease Small pen moved to
when it initially infects only a few birds, you fresh pasture.
may have time to treat the birds with a res-
cue drug or make a management change,
such as moving the birds to fresh pasture.
Early detection requires close observation
and experience. Watch feed intake in par-
ticular—it goes down in the early stages
of coccidiosis.
The choice of production system is an
important management decision. High-den-
sity, large-scale production almost always
requires the use of anticoccidial medica- Portable houses with
tion. In contrast, in low-density, small-scale fence.
production, the birds tend to stay ahead of
the parasites and may not require medica-
tion. Many small-scale producers do not
use anticoccidial medication; however, as
www.attra.ncat.org ATTRA Page 5
6. Brooder and Growout • Put waterers and feeders at a height
level with the backs of the birds, so
Management they cannot defecate or scratch litter
When chicks are brooded in a separate into them. Keep birds from roost-
area before moving them to the growout ing on the feeders with anti-roost-
facility (two-stage production), the brooder ing wire. Suspend waterers or put
stays clean of infective oocysts since fast- them on wire-covered platforms to
growing broilers do not remain past three help keep them clean.
weeks of age. However, chicks are at risk
for coccidiosis if they stay in the brooder • Clean the waterers and feeders
longer than three weeks. Pullet chicks frequently.
for egg laying grow slowly and stay in the • Keep older birds away from chicks,
brooder longer. If chicks are brooded and since old birds are carriers.
grown out in the same facility (one-stage • Add fresh litter or rake litter fre-
production), they seed the area with coc- quently to cover parasites.
cidia. These birds may require a lower den-
sity or, possibly, medication. The following
Litter Management
G
ood brood- management strategies for good brooding
can help. Keep the litter dry to reduce sporulation
ing prac- of oocysts. Remove any wet or crusted
tices can Good brooding practices can reduce the litter. Moisture in the litter is affected by
reduce the need need for medication and include not only the following:
sufficient space but also sanitation and lit-
for medication and • Heat source: A propane radi-
ter management. Give birds adequate floor
include not only suf- space and feeder/waterer space to pre- ant brooder heats a larger area
ficient space but vent overcrowding. Small flock producer and dries out litter more than a
also sanitation and Robert Plamondon recommends at least heat lamp.
litter management. one square foot of floor space per chick • Ventilation: Housing should prevent
and four tube feeders per 100 chicks. drafts but not be airtight. Humid-
(Plamondon, 2003) ity, along with ammonia and other
gases, needs to escape.
• Water leaks: Water leaks must
The chicks are kept in
be prevented.
this brooder for only • Condensation: Condensation may
a few weeks and later
occur in buildings with uninsulated
moved to a growout pen
or small house. roofs and walls and will contribute
to litter moisture.
• Feed: Rations with excessive pro-
tein or excessive salt can result in
wet litter.
Keep the feeders full. If feeders go empty,
birds forage in the litter and ingest oocysts.
The longer they peck at contaminated litter,
the more oocysts they will ingest.
Sanitation
Disinfectants are not effective against coc-
cidia, so sanitation focuses on good hygiene
and removing infected droppings. Keep litter dry by preventing water spills.
Page 6 ATTRA Parasite Management for Natural and Organic Poultry: Coccidiosis
7. In the large-scale industry, “new-house coccidiosis outbreaks in late spring, sum-
coccidiosis syndrome” sometimes occurs mer, and early fall.
when birds are placed on brand-new litter. In the warm, humid South, coccidiosis is a
There is no low-level population of coccidia greater problem than in dry western states.
to establish immunity, so the flock is more Dry conditions on pasture greatly reduce
susceptible, coccidiosis problems are more coccidiosis. In cold areas, although oocysts
likely, and medication may be needed. on pasture may die during winter, the chick-
Some small flock producers are interested ens in the house during winter still carry
in the built-up or composting litter as an oocysts and reseed the pasture with them
ecosystem of microbes. in the spring.
Poultry-house litter becomes significantly It is important to control areas of high traffic
anti-coccidial after about six months’ use, outdoors to reduce the number of oocysts.
as organisms that eat coccidia start to The locations of the waterers and feeders,
thrive and knock down the coccidia popula- the pasture, and the house itself, if possi-
tion… By never removing more than half the ble, should be rotated. Straw, litter, or bark
brooder house litter at a time, it can keep its can help control muddy areas. Controlling
P
anti-microbial properties indefinitely. coccidiosis on pasture is trickier with broil- roducers
(Plamondon, 2002a)
ers than with layers, since the broilers are provide out-
Plamondon recommends starting with at faster-growing and less active. They eat a door access
least six inches of shavings and adding a lot, generating large amounts of manure,
to allow poultry
thin layer of fresh litter on top, which will and congregate in shaded areas. Layers get
off the ground to roost on perches. Keeping to express natural
prevent chicks from eating old litter at first.
birds in a floorless pen that is moved daily behavior, increase
He turns it daily with a spading fork to keep
it from getting packed down and crusted eliminates coccidiosis by breaking the life space, and to pro-
over. If the litter seems too wet, he adds cycle—oocysts cannot re-infect birds. vide fresh air and
more dry litter. He only removes litter sunlight.
when it is too deep to manage or when too Natural Treatments
wet. (Plamondon, 2002b) Keeping birds in general good health is
always important. Some small produc-
Also, although oocysts can be destroyed
ers provide raw milk, yogurt, apple cider
by microbes in the litter and soil, there
vinegar, or probiotics to birds, believing
may be so many oocysts that the birds
that beneficial microbes will prevent or
become infected. Unfortunately, there is lit-
treat coccidiosis. Actually, coccidia do not
tle scientific information available on com- compete with bacteria in the gut; there-
posting litter. fore, beneficial bacteria and other microbes
will not eliminate coccidial development.
Pasture However, anything that improves the over-
Producers provide outdoor access to all health of the gut and the bird can help
allow poultry to express natural behavior, reduce the impact of coccidiosis. Also, a
increase space, and to provide fresh air population of beneficial bacteria is always
and sunlight. Outside, birds may pick up better than pathogenic bacteria, since coc-
fewer oocysts, since they are more likely to cidia weaken the gut wall, and bacteria may
peck forage instead of droppings; however, pass through. In short, feeding dairy prod-
access to the outdoors has both advantages ucts or probiotics will not stop the coccidia
and disadvantages for coccidial control. through “competitive exclusion” but does
Extreme heat and cold outdoors can reduce provide nutrients or beneficial bacteria that
sporulation or kill oocysts. Yet warmth and are useful in any situation.
moisture are favorable conditions for coc- Producers sometimes give diatomaceous
cidia. Before the use of medication, com- earth (DE) to the birds in the belief that the
mercial producers used to experience sharp edges of the fossilized diatoms will
www.attra.ncat.org ATTRA Page 7
8. damage the parasites and reduce coccidio- • Quinolones: Quinolones are “coccid-
sis; however, there is no scientific data to iostats” that arrest the coccidia in
support its use. an early stage of development. An
example is decoquinate (Deccox®).
Drugs The drugs are used for prevention.
Drugs are used for two different purposes: • Ionophores: Ionophores are anti-
coccidials commonly used in the
• To prevent illness large-scale industry. They alter the
• To treat illness function of the cell membrane and
rupture the parasite. Ionophores
Although a producer may depend on man-
also have antibacterial action and
agement for coccidiosis control, a drug such
help prevent secondary gut diseases.
as amprolium is useful for rescue treatment
Ionophores are not synthetic drugs;
in the case of an outbreak. There is no
they are produced by fermentation
need to destroy infected birds; they can be
and include monensin (Coban®)
treated. In large houses, it is necessary to
and salinomycin (Sacox®). How-
routinely use drugs or vaccines because of
D
ever, some ionophores are now com-
rugs are the high density of birds. pletely ineffective against coccidia
used to because of resistance the coccidia
prevent or Types of Drugs have developed. They are used
treat illness. Sulfa • Sulfa drugs: An exciting discovery for prevention.
drugs and ampro- in the 1930s was that sulfa drugs • Other drugs: There are many other
lium treat coccid- would prevent coccidiosis—the first anticoccidial drugs in various chem-
iosis. drugs shown to do so. Sulfa drugs ical classes with various modes
also have some antibacterial action. of action. Examples are Nicarb®
However, a relatively large amount (nicarbizone) and Clinicox®.
of sulfa was needed (10-20 percent
of the diet) and could be tolerated Using Drugs
by the bird for only a short time, You need a veterinarian’s prescription to
since it caused rickets. (Reid, 1990) use drugs for poultry (but not to use vac-
Sulfa drugs had to be used intermit- cines). Feed mills need a license to put
tently (e.g., three days on and three drugs in feed.
days off). Nowadays, comparatively
small amounts of sulfamonaides, In the large-scale industry, drugs are used
such as sulfaquinoxaline, are for prevention rather than treatment. If you
used. They work only against treat the bird after an outbreak, the damage
Eimeria acervulina and Eime- is already done. Many preventative drugs
ria maxima, not against Eimeria are effective only in the first part of the par-
tenella. Sulfamonaides are used to asite life cycle, and therefore must be used
treat coccidiosis. early if they are to be used at all.
• Amprolium: Amprolium is an anti- Drawbacks of using preventative drugs
coccidial drug. It has also been are their expense and the resistance that
used for many years and needs no coccidia have developed. The drugs
withdrawal time to guard against are not as effective now as when they
residue in the meat. It is given in were first introduced. Large companies
the drinking water and interferes use a drug rotation or shuttle program to
with metabolism of the vitamin thia- reduce resistance.
min (vitamin B1) in coccidia. Amp- There are not many new anticoccidial drugs
rolium treats both intestinal and because of the extensive process for FDA
cecal coccidia. approval. It costs millions of dollars to
Page 8 ATTRA Parasite Management for Natural and Organic Poultry: Coccidiosis
9. develop a new anticoccial drug and get it is produced by Schering Plough
approved for use. Animal Health.
In the large-scale industry, most anticoc- • Immucox®: This vaccine was devel-
cidial drugs are withdrawn a week before oped in Canada by Vetech Labora-
slaughter of broilers to save money or to tories. It is distributed by Wingo.
prevent residue in the meat. Drugs are • Advent®: This vaccine was recently
withdrawn before layers begin laying eggs developed in the U.S. by Viridus
to prevent residues in the eggs. Animal Health. It is marketed as
Small producers often give pullets medi- having more viable oocysts (truly
cated feed while in the brooder, and then sporulated oocysts that can cause
remove medication when they are older and immunity) than other vaccines.
placed in pasture-based systems. The vaccines above can actually cause
some lesions and occurrence of coccidio-
Unfortunately, drugs used for preven-
sis in birds because they are not “attenu-
tion usually interfere with development of
ated” or weakened in some way. It is a con-
immunity to coccidia. On the other hand,
trolled occurrence, but it may be necessary
V
using drugs for treatment only does allow accines are
to treat for secondary gut disease, using
immunity to develop. If signs of the disease
antibiotics or alternatives such as probiot- recognized
appear, use drugs that are appropriate for
ics. In contrast, coccidiosis vaccines used as the only
coccidia’s late life cycle—only sulfonamides
in Europe are attenuated. They are altered practical alterna-
and amprolium. (Reid, 1990) When birds
because the coccidia used in the vaccine
are getting sick, they lose their appetite. tive to anticoccidial
are designed to mature quickly and have a
Therefore, soluble medication should be drugs in large-scale
short (“precocious”) life cycle and low fer-
provided in the drinking water. production.
tility. They are not pathogenic—disease-
causing—and are more costly to produce
Vaccines than the nonattenuated vaccines. They
Interest is growing in controlling coccidio- include Paracox®, Livacox®, and Viracox®
sis by vaccination because immunological which are marketed in other countries but
control is recognized as the only practical not currently in the U.S.
alternative to anticoccidial drugs in large-
More types of vaccines are likely to be devel-
scale production. (Chapman, 2002)
oped, because the government approval pro-
La rge pou lt r y compa n ies usua l ly cess is much cheaper for vaccines than for
vaccinate chicks at company-owned hatch- anticoccidial drugs.
eries. Smaller producers buy chicks from
Since immunity is species-specific, anticoc-
independent hatcheries, but some hatch-
cidial vaccines include mixtures of species
eries do not offer coccidiosis vaccination.
of Eimeria that affect chickens. It is espe-
Small producers may need to do the vac-
cially important to include the three types
cination themselves, once the chicks arrive
that cause the most damage in chickens:
at the farm.
Eimeria acervulina, Eimeria maxima, and
Eimeria tenella.
Types of Vaccines
At the time of this writing (2006), coccid- Using Vaccines
ial vaccines licensed in the U.S. include
Birds need good protection by the time they
the following:
are three weeks old, so vaccines should be
• Coccivac®: This vaccine was devel- given at the hatchery or by one week.
oped in the early 1950s. The “B”
Methods of application:
and “D” types are different mix-
tures of Eimeria species; the “T” • Spray cabinets: These are used at
type is for turkeys. Coccivac® hatcheries on day-old chicks and
www.attra.ncat.org ATTRA Page 9
10. may include a dye to indicate appli- Vaccines are usually sold only in large
cation. This is the most uniform amounts. Advent is sold in 1,000-dose
method of application, resulting in vials that cost about $13.50 each and must
90 to 95 percent of chicks exposed be purchased in boxes of 10 vials per box.
to the vaccine. (Chapman, 2000) Immucox can be purchased in smaller
• Edible gel: Gel pucks are placed in amounts. A tube of gel costs about $70
transport crates or on the floor of and has 28 “slices.” Each slice serves 100
the house when the chicks arrive. birds. Half tubes can also be purchased
The gel is brightly colored to attract for about $35.
the attention of the chicks. Immu-
Since the vaccines contain live oocysts, they
cox® is administered in this form.
should not be frozen. Birds need access
• Feed spray: Vaccines are mixed with to their droppings in order for the vaccine
water in a garden pressure-sprayer to work, since oocysts must be reingested.
and sprayed on a 24-hour supply of Vaccines are not effective for birds raised in
feed. Advent® is either sprayed on batteries or cages with wire floors.
the feed in this manner or applied
I
in a spray cabinet at the hatchery. Vaccines have been used for some time to
t is important to
• Drinking water: The chicks should provide immunity for broiler breeders and
apply vaccines
be slightly water-starved to encour- commercial egg layers, but there is less use
uniformly to in broilers.
age them to drink. Since oocysts
ensure the birds get are heavy and fall to the bottoms Vaccine boosters are not normally given.
equal exposure. of drinkers, they are mixed with Broilers usually have a short life and do not
a suspension agent to keep them need boosters. Longer-lived birds like lay-
evenly distributed. (Chapman, ers are constantly re-exposed to coccidia,
2000) This method can be used for
so immunity is topped off constantly.
older chicks. Vaccines cannot
be given through proportioners or Do not give drugs and vaccines to the same
nipple drinkers. flock—they are opposed to each other.
To confirm the method of application, check If your flock is raised under intensive con-
the tag. For example, Coccivac® is given to ditions, you will eventually need to vacci-
turkey poults by spray cabinet at 1 day old; nate or use drugs. Tips for using vaccines
feed spray at 1 to 3 days old, and via drink- in large-scale production are provided in
ing water from 3 to 14 days old. the sidebar. Although most large poultry
It is important to apply vaccines uniformly companies work with their veterinarians on
to ensure the birds get equal exposure. If health issues, these tips will be useful.
birds receive too much of a nonattenuated
vaccine, the parasites can cause lesions. Summary
If attenuated vaccines are not given in
adequate doses, the birds will be sus- Small-scale producers can control coccid-
ceptible to field strains of the coccidia. iosis with a good understanding of its life
(Chapman, 2000) cycle and conditions for transmission, by
management strategies such as good litter
The environment must allow the oocysts and pasture rotation, and by using drugs
to sporulate, since the goal of vaccination only for rescue, if needed. Large-scale
is to introduce the parasite in small num- producers, especially organic producers,
bers. Litter should be damp but not wet. increasingly rely on vaccines.
(Chapman, 2000) After vaccination, birds
excrete fresh oocysts onto the litter. Birds For more information, contact Anne
then eat these (second cycle) oocysts. (Chap- Fanatico at annef@ncat.org.
man, 2000) Two cycles of replication are
needed for good protection.
Page 10 ATTRA Parasite Management for Natural and Organic Poultry: Coccidiosis
11. Tips for Using Vaccines in Large-scale Production
“Partial house” brooding and brooder rings can cause problems for coccidiosis management in large-scale production. In
partial-house brooding, part of the house is sectioned off for brooding, while the rest of the house is vacant. Therefore, the
whole house is not seeded with a low level of oocysts to help establish immunity. Producers should either release broilers
to the whole house before 6 days of age or hold them until 12 days. (Chapman, 2002)
Although organic companies cannot use routine drugs, it is important to know about drug/vaccine interactions. The conven-
tional poultry industry uses vaccines in combination with drugs to help deal with the problem of drug resistance in broilers.
Sensitivity testing can determine the level of resistance. Vaccines are prepared with coccidia strains that are susceptible to
drugs. The vaccinal coccidia reproduce with field-strain coccidia in the broiler house and transfer drug susceptibility to drug-
resistant strains. Vaccines essentially seed a house with coccidia that are sensitive to drug use. Therefore, large producers rotate
drugs with vaccines to restore drug sensitivity to the field strains or replace the field strains with drug-sensitive strains.
Since the nonattenuated (unweakened) vaccines can cause lesions, pathogenic bacteria can enter the gut. You may need
to treat for necrotic enteritis at 16 to 17 days with an antibiotic. (Chapman, 2002) These secondary bacterial infections are a
particular problem for organic companies. Treating birds with antibiotics for necrotic enteritis means removing them from
the organic program. Fortunately, there are natural alternatives to antibiotics, such as probiotics. It is also important to con-
trol factors that predispose birds to necrotic enteritis, such as feeding fishmeal. Poor uniformity of vaccine application and
partial-house brooding or brooder rings can increase the incidence of complications.
References Long, P.L. 1968. The effect of breed of chickens on
resistance to Eimeria infections. British Journal of Poul-
Chapman, D. 2000a. Practical use of vaccines for the try Science. Vol. 9. p. 71-78.
control of coccidiosis in the chicken. World’s Poultry
Science Journal. Vol. 56. p. 7-12. Merck Manual On-Line
www.merckvetmanual.com/mvm/index.jsp
Chapman, D. 2002b. Sustainable coccidiosis con-
trol in poultry production: The role of live vaccines. Organic Livestock Research Group. 2000. Coc-
International Journal for Parasitology. Vol. 32. p. 617- cidiosis. In: Poultry Health and Welfare in Organic
629. Farming. Veterinary Epidemiology and Eco-
nomics Research Unit (VEERU), Department
Farr, M.M., and E.E. Wehr. 1949. Survival of Eimeria of Agriculture, The University of Reading, U.K.
acervulina, E. tenella, and E. maxima oocysts on soil www.organic-vet.reading.ac.uk/Poultryweb/disease/
under various field conditions. Annual N.Y. Academy coccid/coccid1.htm
of Science. Vol. 52. p. 468-472.
Plamondon, Robert. 2003. Re: Probiotics (Also Coc-
cidiosis). E-mail posting to PasturePoultry listserver.
March 1.
Plamondon, Robert. 2002a. Re: Coccidiosis. E-mail
posting to PasturePoultry listserver. December 20.
Plamondon, Robert. 2002b. Coccidiosis control. E-
mail posting to PasturePoultry listserver. April 3.
Reid, Malcolm, W. 1990. History of avian medicine
in the United States. X. Control of coccidiosis. Avian
Diseases. Vol. 34. p. 509-525.
Further Resources
Buvanderan, V., and P. Kulasegaram. 1972. Resis-
tance of breeds and breed crosses of chickens to
experimental Eimeria necatrix infection. British Vet-
erinary Journal. Vol. 128. p. 177-183.
www.attra.ncat.org ATTRA Page 11