I. Clinical Symptoms and Production Indicators
In pullets beginning to lay, the laying rate rises slowly or stops increasing, often hovering around 80%, while feed intake remains low. As soon as the flock reaches peak production, the laying rate begins to decline slowly; egg weight is low, and eggs are small. About 10%–15% of hens have pale combs that droop. In high-producing hens, eggshell color becomes lighter. Brown-shelled eggs that turn white (noticeably) account for approximately 10%–30%, with variation.
In laying flocks, a small proportion of hens develop diarrhea, followed first by prolapse and then vent pecking, with an increase in deaths. The flock's droppings are loose and reddish, with feed present. Treatment for enteritis, small-intestinal coccidiosis, and enterotoxemia syndrome is given, but the condition repeatedly recurs despite multiple courses of medication and does not resolve for a long time.
II. Clinical Misdiagnosis and Analysis of Causes
Because tapeworm infection in chickens progresses slowly and clinical signs appear gradually, cases occur more frequently from 6 to 11. In particular, when temperatures drop from 10 to 11 and egg production declines, the condition is often mistakenly attributed to the drop in temperature in clinical practice. It is commonly treated as a viral disease or mild avian influenza, but repeated medication is ineffective.
Tapeworms parasitize the intestines. Their scolex attaches to the intestinal mucosa, damaging the integrity of the intestinal wall and causing hemorrhagic enteritis. The fecal symptoms resemble those of enterotoxemia syndrome, and treatment for enteritis or enterotoxemia syndrome alone usually cannot cure the condition. Carefully observe the feces. Characteristic feces caused by tapeworms are red or rust-colored and resemble “sorghum grains,” with white “sesame seed-like” tapeworm segments visible on them. After effective tapeworm treatment, sorghum-like feces and egg production return to normal within 7–10 days, with no recurrence.
III. Tapeworms
1. Tapeworm morphology and species
Tapeworms are ribbon-shaped, flat, and mostly milky white. The body is divided into a scolex, neck, and segments. The scolex is an attachment organ that attaches to the host’s intestine. The neck develops and produces segments. According to their stage of development, the segments are classified as immature, mature, or gravid (egg-bearing segments).
Common tapeworms in chickens include Raillietina cesticillus, Raillietina tetragona, Raillietina echinobothrida, Davainea proglottina, and Hymenolepis. The common tapeworm in waterfowl is Fimbriaria fasciolaris.
2. Life cycle and development
Adult tapeworms parasitizing the chicken intestine pass gravid segments in the feces. After these are ingested by an intermediate host, they develop into cysticercoids in its body over 2–4 weeks. After a chicken ingests an intermediate host containing cysticercoids, the tapeworm develops into an adult in the small intestine in as little as 13–14 days and sheds mature segments. Waterfowl tapeworm eggs develop into cysticercoids inside an intermediate host in about 6 weeks. After a duck or goose ingests a copepod, the tapeworm develops into an adult in about 19 days.
3, the intermediate hosts of chicken tapeworms
The intermediate hosts of chicken tapeworms include ants, flies (maggots), slugs, snails, and beetles such as scarab beetles and ground beetles. At present, caged laying hens mainly come into contact with flies (maggots) and beetles as intermediate hosts. Chicken tapeworm infection is closely related to intermediate hosts, so controlling and reducing intermediate hosts can help prevent tapeworm infection.
4, the current prevalence of chicken tapeworm disease
Chicken tapeworms are widely distributed, which is related to the widespread presence of intermediate hosts such as ants, flies, and beetles of the order Coleoptera. Free-range chickens are infected and develop disease throughout the year. Caged laying hens are often infected and develop disease from 6 to 11 each year. In summer and autumn, infection is mostly at the cysticercoid stage; in late autumn and early winter, disease is mostly caused by infection with adult tapeworms. At present, the disease mainly occurs during the laying period. Many laying hens carry tapeworms, resulting in a significant decline in egg production or death, intestinal inflammation, and hemorrhagic enteritis. Pullets and chicks are most susceptible to infection and have a high mortality rate.
5, symptoms of tapeworm infection
In pullets, feed intake decreases, water consumption increases, weight gain slows, flock development is delayed, and uniformity is poor. Sick birds appear listless, with ruffled feathers and pale combs and wattles; they become emaciated and die. Laying hens show digestive disorders, emaciation, and anemia, and feather pecking and pecking at the vent become more common in the flock. Eggshell color and hardness, as well as yolk color, deteriorate, and eggs become smaller. Egg production stops increasing or declines markedly.
Hemorrhagic enteritis: The tapeworm scolex penetrates into the submucosa of the intestine, damaging the intestinal mucosa and forming nodular lesions, which cause hemorrhagic enteritis. The feces are loose and contain pale yellowish-white, bloody mucus; formed feces may be reddish-brown and interspersed with grain-like material. On fecal examination, gravid proglottids are found in the feces. The segments range in size from sesame seeds to grains of rice and are milky white; sometimes, the segments can be seen moving. Neurological symptoms: Metabolic products of the worms can cause autointoxication in sick birds, resulting in neurological symptoms such as convulsions.
Necropsy findings: The small-intestinal mucosa is thickened and congested, and adult worms may be found. At the sites of parasitism, there are pinpoint-sized nodular lesions with depressed centers. When large numbers of worms accumulate, they can cause intestinal obstruction, which may lead to intestinal rupture and peritonitis. Severe cases can result in death.
IV. Current Status of Chicken Tapeworm Disease Prevention and Control and Misconceptions About Medication
In recent years, poultry tapeworm infections have generally been managed with benzimidazole anthelmintics—levamisole and albendazole—as regular preventive deworming medications. During treatment, the medication needs to be administered again one week later. Moreover, it cannot completely eliminate the worm’s scolex, which is related to the development of anthelmintic resistance in tapeworms.
Some farms also use macrolide disaccharide anthelmintics—avermectin and ivermectin—for regular preventive or therapeutic deworming. However, this class of drugs has no anthelmintic effect against tapeworms. Consequently, after preventive deworming, the tapeworm problem may be overlooked, and a lack of observation can lead to tapeworm disease.
Praziquantel has been used for many years in some regions, where drug resistance is commonly observed and deworming efficacy is unreliable. When selecting anthelmintics, factors to consider include whether they can completely eliminate the worm’s scolex and larvae, and their effects on the laying performance of adult chickens, among other issues.
V. Tapeworm Prevention and Control
Regular deworming: Deworm pullets at 60 days of age and pullets just beginning to lay at 120 days of age, once each. For adult laying hens, administer preventive deworming once in 5 and once in 8. Since summer and autumn are seasons when the intermediate hosts—flies and beetles—reproduce in large numbers, and a period when laying hens become infected with tapeworms, deworming in 8 is especially important.
Biosecurity: Remove chicken manure frequently and compost it to kill the eggs in gravid proglottids. At the start of the fly breeding season, add cyromazine to the feed to inhibit maggot breeding. Regularly control ants, scarab beetles, and other beetles outside the chicken house to reduce intermediate hosts.