Important Internal Parasites of Poultry

Alok Kumar Singh1#, Snigdha Shrivastava2, B. Dasmabai3,Shailendra Singh4 and Pallabi Pathak5

1Department of Veterinary Parasitology, College of Veterinary Science & A.H., Rewa
2Ph.D. Scholar, Department of Veterinary Medicine, COVSc& A.H., Rewa
3Department of Veterinary Parasitology, College of Veterinary Science, Rajendranagar
4Department of Veterinary Pathology, College of Veterinary Science & A.H., Rewa
5Department of Parasitology, Lakhimpur, COVSc, AAU, Joyhing, North Lakhimpur, Asam

Internal Parasites are basically classified into two groups i.e.helminths and protozoa. The parasitic diseasediffers from other bacterial and viral disease in many ways:

  • As parasites have complex lifecycle.
  • Transmission of parasites from bird to bird is different than that of otherbacteria or viruses.
  • Disinfection and quarantine are of little use for controlling the parasites.
  • Blood analysis is not suitable for diagnosing parasites.
  • The advanced commercial confinement systems have played an important role for reducing the incidence of worm infection by limiting the accessof birds to many parasites as alternate hosts.
  • On the other hand, high stocking density andconfinement systems led to an increase in the incidence of protozoan parasite in the flocks.
  • Worms are common in free-range and backyard flocks. Generally low levels of parasitism does not cause the harm.
  • In severe casesitleads to significant losses of feed efficiency, production and health status.
  • Severe infection not only decrease the efficiency, but also makes more susceptible to other diseases.

Helminthes (Worms)

Ascarids:Large Roundworms

  • Ascarids are the most damaging worms common in backyard reared flocks. Moreover, mild infection of ascarids are often unnoticed, but severe infection may cause intestinal blockage, reduction in nutrient absorption and even death.
  • Severity of infection not only makes the birds less efficient, as well as makes them more susceptible to other disease.
  • Thickness of ascarids about a pencil lead and may grow approximately four and half inches long.
  • Easily seen with the naked eye and occasionally migrate into reproductive tract of hen’s and become encased in a newly forming egg.
  • Life cycle is direct, which means that the parasite eggs are found in the droppings of infected birds which are further takeup bysusceptiblebirds through contaminated feed, water or faeces.
  • Clinical signs of ascarids infection mainly includes;diarrhoea, lethargyand weight loss in affected birds.
  • Control measures for the prevention of large roundworms infection includes; complete cleaning of housing between the different groups of birds, strict sanitation and segregation of younger birds. Provide clean range for each group of birds definitely helps to reduce the level of infection in flocks.

Heterakisgallinarum (Caecal Worms):

  • It is a common parasite of backyard poultry rearing flocks.
  • As the name indicate, the worms inhabits in the caecum of the infected bird.
  • May cause little or no damage to poultry flocks but it act as a carrier of organism that causes blackhead disease in turkeys.
  • In backyard poultry farming, earthworms are commonly occur in premises and theyingest the infected caecal worm egg from poultry litter,after consumption of such earthworms by turkey become infected with the blackhead disease.
  • The susceptible turkeys may also become infected with the blackhead organism from direct contact byoral ingestion of the infected caecal worms.
  • Therefore, turkeys and poultry shouldnot be housed together, as well as turkeys shouldnot allowed to range where poultry hasalready ranged.

Capillaria(Thread Worms):

  • Several species of Capillariathat infect to the poultry. Itaffect different parts of the birds and causing various symptoms.
  • Those species occurs in the crop and oesophagus region, causes thickening and inflammation of the mucus membranes.
  • It causes severe losses in turkeys and other game birds.
  • While, other species are prevalent in the lower intestinal tract and causeshaemorrhage, inflammation and erosion of the intestinal lining. Death may occur in severe infected birds.
  • It has both direct life cycle as well as indirect lifecycle.
  • Capillariainfection is a common problem of deep bedding houses and heavy infections causes reduction in growth, egg production and reduced fertility.


  • The size of tapeworms varies from very small mm to centimetre.
  • Each species attaches to a different part of the digestive tract using four pairs of suckers situated on their heads and mostly are host-specific.
  • It requireintermediate host for completion of their lifecycle.
  • The intermediate hosts are; ants, beetles, houseflies, slugs, snails and termites.
  • It is made up of multiple flat sections and shed in groups of two to three on a daily basis.
  • Every section contains hundreds of eggs and each tapeworm is being capable of shedding millions of eggs in its whole life.
  • Control can be achieved by controlling the intermediate host, but it is impractical because of differencehousing systems.
  • Tapeworm parasites require anintermediate host to complete their lifecycle such as; ants, beetles, houseflies, slugs, snails and termites.


  • Protozoan parasites are single celled, found in all habitats, and found in both domestic animals and humans. Several phyla or families of protozoa, out of which two are importance to the poultry sector andit includes intercellular protozoa, flagellates and amoeba. 


  • Coccidiosis is a disease caused by intestinal protozoan parasite of thepoultrybelongs togenus Eimeria, commonly referred as coccidia.
  • Nine species of Eimeriaaffect the birds.
  • Coccidia is much host specific which means,coccidia that affect thepoultry would not affect the other livestock.
  • Coccidian parasites inhabits and reproduce in the digestive tract, where it causes tissue damage.
  • The damage in the digestive tract resultsreduction in nutrient and fluid absorption and causes diarrhoea and loss of blood.
  • The disease may increase susceptibilityof infected bird’s to other important poultry diseases.
  • Coccidianparasites are found everywhere. Chicks develop immunity over time and period between3-6 weeks of age is the most susceptible age for occurrence of disease.
  • The clinical signs includes; bloody and watery diarrhoea, loss of weight, lethargy, ruffled feathers and general malaise.
  • Anticoccidial added feeds provide control but unable to eliminate coccidian, so, allowing the young birds to develop resistance againstcoccidian, most prevalent in environment.
  • The disease may be controlled by involvement of good sanitation, adequate nutrition, ample quantity clean water and dry bedding.
  • Those birdswhen housed in a floor based system are exposed against coccidia all their lives but properly fed and managed, will develop resistance.
  • Birds whoever raised in cagesystem are not exposed to the infective organismdue to which no development of resistance in them.
  • Good management and proper vaccination provide disease free environment.
  • Caution when the birds are vaccinatedagainst coccidiosis, then they should not be offered anticoccidial feed as the coccidiostat may kill the modified organism present in the vaccine.


  • It is a form of coccidia, caused by Cryptosporium baileyi.
  • It is not host specific means those causes in poultry can infect other birds.
  • Cryptosporium baileyimay spread frequently from flock to flock by feet of animals as well as people and also carried by wild birds.
  • The symptoms caused by intestinal cryptosporidiosis are includes; pale skin occurred in the in the yellow skinned breeds.
  • The disease is also spread by inhalation, which results in respiratory infection and is more severe as compared with intestinal form.
  • Younger birds up to four months age are more susceptible to respiratory form of the disease.
  • There is no effective treatment, onlysupportive treatment is given to check the development of secondary infection.
  • Recovered birds generate the immunity to further infection.


  • Commonly called as blackhead disease and causes serious disease of turkeys.
  • Poultry carry and pass the organism but are generally immune.
  • Range raised birds are most susceptible for blackhead disease.
  • The susceptible birdsare eaten an earthworm carrying the infective eggs of the caecal worm, which has been infected with the histomonad parasite.
  • The parasite infects to the caecum of the poultry and shed in the eggs of the caecal worm.
  • The close rearing of turkeysto poultry or susceptible range who, infected with the caecal worm eggs will pick up the infection and develop the disease.
  • It cannot survive longer in the environment unless they are protected within a caecal worm egg orinside the body of an earthworm.
  • Preventive and control measures involves controlling caecal worms to reduce the spread of the parasite as well as also to advised not to be reared in the areas that previously contained birds.

Prevention and Control Measures:

  • The internal parasites do not cause significant harm at low levels of infection.
  • Provide proper attention to housing, nutrition and alternate host control, and the chances of parasite infection can be minimize.
  • Some points to helps in prevention and control of internal parasites in poultry.
  • Kept the bedding in the flock as dry as possible as wet bedding is more favourable for bacteria and parasite carrying organisms.
  • Kept the clean flock and areas where poultry reared because lack of cleanliness is a common reason for development of disease.
  • Complete cleaning and sanitize the flock before introducing to a new birds, it helps to decrease the chances of the next flock being infected with what the earlier flock had.
  • Provide clean waterers daily and change the bedding regularly because a clean flock is a healthy flock.
  • Avoid overcrowding as it will helps to reduce the number of birds that contract parasites and keep flock cleaner.
  • Restrict the entry of pigeons, wild birdsand other birds away from poultry, as several internal parasites are transmissible among the birds.
  • Shedding the worm eggs in their faecal matter by infected birds
  • Kept birds off where the chance of ingestion of earthworms and other insects because it act as alternate hosts to internal parasites that affect poultry.