External parasites in poultry are a current problem and they generate significant economic losses in the world’s poultry industry.

Ectoparasites in poultry

Numerous diseases can affect the health and production of laying hens or broilers. An important group is parasites and, specifically, external parasites (ectoparasites). Ectoparasites are a group of arthropod animals that, in addition to directly causing injury, can transmit pathogenic agents such as bacteria, viruses, and fungi.

In poultry, ectoparasite problems are prevalent. In laying hens, they cause cause decreased egg production, anemia, discomfort, weight loss and mortality. At broiler chicken, they generate a decrease in weight gain.

Eventually, the control of ectoparasites in poultry is difficult because of their resistance to antiparasitics. Some of them are also resistant to adverse environmental conditions.

Mites

1. Red bird mite

   1. Etiology: The bird’s red mite is the Dermanyssus gallinae. It is also known as the hen’s mite. The name ‘red mite’ is due to the coloration acquired by the parasite after feeding the blood of birds.
   2. Cycle: The female mites feed constantly blood of the hens. After this, they lay eggs on the bird. These eggs hatch and, the hexapod larvae emerge (with six legs), which do not feed blood. Then, larvae become nymphs that have eight legs. Nymphs feed the blood during the night while they hide in the shed during daytime. Then, they become adults and the cycle starts again.
   3. Clinical signs: This poultry mite remains in the beds or cracks of the shed during the daytime. During the night, it moves and goes up to the hens to feed. It leads to a decrease of the laying rate of 25%. Being a hematophagous mite, it consumes blood from birds, causing anemia and progressive weight loss. In addition, it can transmit species of Salmonella bacteria during the bite.
   4. Diagnosis: Mites are found in the feathers of birds during the night. Mites are recognized by their reddish color. We can also obtain diagnosis with samples of soil dust where the parasite rests during the day. Less often, the histopathology can show perivascular eosinophilic infiltration of the superficial dermis.
   5. Treatment and control: the treatment should focus on environmental control of the mite. Most of the time, the mite remains hidden between cracks and slits in the shed. For this, acaricide treatments should be applied when the shed is in the rest period, without birds. Taking into account that mites can survive without eating for many months and can be resistant to antiparasitics, sanitization should be done several times when the shed is resting.
   6. Importance: It is the most important ectoparasite of poultry production in the world, especially of laying hens. On the other hand, it is a zoonotic parasite. It can infect other birds such as pigeons, turkeys, and wild birds; also mammals, including humans too.

2. Scabies of the legs

   1. Etiology: Knemidocoptes mutans causes scabies of the legs, also called «scab of the legs», «calcareous legs», or «elephantiasic legs» due to the injuries generated.
   2. Cycle: the transmission of the parasite is by contact. The female is viviparous and deposits the larvae on the skin of the bird. They later become nymphs and adults; most of the time on the animal. The mite infests the feet of birds between the scales. After causing lesions, the parasite falls together with the scabs to the ground. When another bird tramples on these scabs, the mite climbs through its feet.
   3. Clinical signs: Birds with Knemidocoptes mutans have noticeable lesions on the legs. The excavation of the parasite in the skin generates exudates, flaking, dryness, and scabs on the legs. Injuries usually start with the fingers and go up. The bird may end up with claudication, and in more severe cases with arthritis and prostration.
   4. Diagnosis: the diagnosis is based on the signs seen on the legs. A scraping of the skin or scales can be sent to the laboratory to look under a microscope. The mites Knemidocoptes mutans are characterized by a roundish form and short legs.
   5. Treatment and control: Initially, isolate affected birds to prevent transmission of the parasite to healthy birds. Then, clean the legs of the affected birds, removing the injured scales. To directly treat the lesions, apply intramuscular or topical ivermectin. Besides, environmental control is carried out through the application of acaricide products in the shed.

Ticks

1. Soft tick of birds

   1. Etiology: The main tick affecting birds is Argas persicus.
   2. Cycle: Female Argas ticks feed on the blood of birds. With the nutrients obtained, they make their oviposition and, after weeks, the larvae emerge. These larvae look for the hens to climb up and feed on them. Then, they turn into nymphs that continue to feed the blood. They finally grow up to adults.
   3. Clinical signs: Infestation by soft ticks in birds causes severe anemia. Animals with anemia look pale, weak, prostrate, have lower laying rate, and weight gain is affected. Ticks are transmitters of other pathogens such as bacteria, hemoparasites, and rickettsias.
   4. Diagnosis: ticks are diagnosed by direct observation of the parasite on birds. Send ticks to a laboratory to confirm the diagnosis.
   5. Treatment and control: implement integrated tick control is recommended. For this, apply chemical methods such as antiparasitic organophosphates, carbamates, or pyrethroids. Besides, implement environmental and biological control is advised. This control includes making complete sanitization of the sheds in rest periods, to eliminate stages such as eggs, larvae, nymphs, and adults. The farm must control the entry of wild birds to prevent ticks from entering the shed.

Lice

Lice are a group of parasites that affect poultry production regularly. There are several species involved that here are named equally under the name pediculosis, meaning lice infestation.

1. Pediculosis in poultry

   1. Etiology: Cuclotogaster heterographa (head lice), Lipeurus caponi (wing lice), Menopon gallinae (wing lice) Menacanthus stramineus (body lice). The lice in birds are varied and are distinguished by their preferred location in the infested bird.
   2. Cycle: Lice perform their entire cycle on the bird; for this reason, the transmission occurs by direct contact between birds. Adult females lay eggs at the base of the feathers, commonly called nits. From the nits hatch larvae that later transform into nymphs. Then, they become adults.
   3. Clinical signs: lice often eat debris on the skin of birds. However, their presence causes injuries that can lead to bleeding; lice feed on the wounds. In the long term, pediculosis generates weakness, anemia, prostration, decreased egg production.
   4. Diagnosis: Diagnosis can be made by direct observation of lice between feathers. Another possibility is to collect feathers from birds and sending them to the laboratory to confirm their presence.
   5. Treatment and control: the lice live all the time on birds; therefore, the treatment is done on them. Environmental management can be a complement, preventing the entry of external birds. Pyrethroids are a group of antiparasitics that can be applied in powder or spray on birds. Consider the withdrawal time; avoid poisoning though they are safe.

Conclusions

External parasites can generate severe clinical symptoms in infested birds. Besides, their presence translates into a negative impact on egg or meat production in poultry. It is essential to monitor their appearance for appropriate and timely control and treatment.

References:

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