# [Poultry Parasites](/knowledge/parasites/avian-parasites/internal-external-parasites-poultry-worms-mites-protozoa-chickens): Mites, Lice, and Internal Parasites Including Those Transmitted via Eggs

## Key Takeaways

- Poultry are susceptible to a broad spectrum of ectoparasites (mites, lice, ticks, fleas) and endoparasites (nematodes, cestodes, trematodes, protozoa), with significant impacts on health, productivity, and food safety.
- Hematophagous mites like *Dermanyssus gallinae* cause anemia and reduced egg production, while also acting as vectors for bacterial pathogens such as *Salmonella*.
- Nematodes, particularly *Ascaridia galli* and *Heterakis gallinarum*, are prevalent intestinal parasites; *H. gallinarum* is a critical vector for *Histomonas meleagridis*, the causative agent of histomonosis.
- Coccidiosis, caused by *Eimeria* species, is a major protozoan disease characterized by diarrhea and reduced feed conversion, with resistance to anticoccidials being a significant concern.
- Vertical transmission of parasites can occur via eggs, with *Capillaria* species and *Prosthogonimus* flukes being examples that can contaminate egg contents or oviducts.
- Diagnostic approaches integrate fecal flotation for helminth eggs and coccidian oocysts, necropsy for direct visualization, and molecular methods like PCR for precise pathogen identification.

---

## Introduction

Poultry production systems are susceptible to a diverse array of parasitic organisms that compromise bird health, welfare, and productivity. These parasites are broadly classified into ectoparasites (mites, lice, ticks, fleas) and endoparasites (nematodes, cestodes, trematodes, protozoa). A subset of these parasites can be transmitted vertically through the egg or horizontally via contaminated meat, posing risks to both flock health and [food safety](/knowledge/bacteria/livestock-bacteria/cooking-chicken-bacteria-prevention) [<a href="#ref-1">1</a>, <a href="#ref-2">2</a>]. This article provides an exhaustive review of the major parasitic groups affecting poultry, with emphasis on their biology, clinical impact, diagnostic approaches, and control strategies.

## Ectoparasites: Mites and Lice

### Mites

Mites are among the most economically significant [ectoparasites of poultry](/knowledge/parasites/avian-parasites/poultry-ectoparasites-dermanyssus-ornithonyssus-knemidocoptes-argas). The poultry red mite, *[Dermanyssus gallinae](/knowledge/parasites/avian-parasites/dermanyssus-gallinae)*, is a hematophagous mite that feeds on blood at night and hides in crevices during the day [<a href="#ref-3">3</a>]. Infestations cause anemia, decreased egg production, and increased mortality. *D. gallinae* is also a vector for bacterial pathogens such as *[Erysipelothrix rhusiopathiae](/knowledge/bacteria/livestock-bacteria/erysipelothrix-rhusiopathiae-swine-erysipelas-arthritis-diamonds)* and *Salmonella* species [<a href="#ref-3">3</a>]. The northern fowl mite, *[Ornithonyssus sylviarum](/knowledge/parasites/avian-parasites/ornithonyssus-sylviarum-northern-fowl-mite-poultry)*, is a permanent resident on the host, causing severe irritation, feather damage, and reduced feed conversion efficiency [<a href="#ref-4">4</a>]. The scaly leg mite, *[Knemidocoptes mutans](/knowledge/parasites/avian-parasites/knemidocoptes-mutans-scaly-leg-mite-chickens-treatment)*, burrows into the keratin of the legs and feet, causing hyperkeratosis, crusting, and lameness [<a href="#ref-1">1</a>, <a href="#ref-4">4</a>]. *[Knemidocoptes gallinae](/knowledge/parasites/avian-parasites/knemidocoptes-gallinae-depluming-mite-chickens)* (depluming mite) causes feather loss and skin irritation [<a href="#ref-1">1</a>].

### Lice

Lice (Mallophaga) are obligate ectoparasites that feed on feathers, skin debris, and blood. Common species include *Menacanthus stramineus* (body louse), *Menopon gallinae* (shaft louse), *Lipeurus caponis* (wing louse), and *Columbicola columbae* (pigeon louse) [<a href="#ref-1">1</a>, <a href="#ref-2">2</a>]. Lice infestations cause feather damage, reduced growth rates, and decreased egg production. Heavy infestations can lead to anemia and death in young birds [<a href="#ref-4">4</a>]. Lice are host-specific and are transmitted by direct contact or through contaminated fomites.

### Ticks and Fleas

The fowl tick, *[Argas persicus](/knowledge/parasites/avian-parasites/argas-persicus-fowl-tick-poultry-spirochetosis)*, is a soft tick that feeds on blood and transmits *[Borrelia anserina](/knowledge/bacteria/avian-bacteria/borrelia-anserina-avian-spirochetosis)* (avian spirochetosis) [<a href="#ref-1">1</a>, <a href="#ref-5">5</a>]. *Ornithodoros moubata* is another soft tick species reported in African poultry systems [<a href="#ref-1">1</a>]. The sticktight flea, *Echidnophaga gallinacean*, attaches to the skin around the head and eyes, causing irritation and secondary infections [<a href="#ref-1">1</a>].

## Internal Parasites: Nematodes, Cestodes, and Trematodes

### Nematodes

Nematodes are the most prevalent endoparasites in poultry. *Ascaridia galli* (large roundworm) resides in the small intestine, causing malnutrition, reduced growth, and decreased egg production [<a href="#ref-6">6</a>, <a href="#ref-7">7</a>]. *[Heterakis gallinarum](/knowledge/parasites/avian-parasites/heterakis-gallinarum-cecal-worm-histomonas-vector)* (cecal worm) is a common nematode that can carry *[Histomonas meleagridis](/knowledge/parasites/avian-parasites/histomonas-meleagridis-blackhead-disease-turkeys)*, the agent of histomonosis (blackhead) [<a href="#ref-6">6</a>, <a href="#ref-8">8</a>]. *Capillaria* species (hairworms) infect the crop, esophagus, and intestine, causing severe enteritis and weight loss [<a href="#ref-7">7</a>, <a href="#ref-8">8</a>]. *[Syngamus trachea](/knowledge/parasites/avian-parasites/gapeworm-syngamus-trachea-poultry-game-birds-diagnosis-treatment)* (gapeworm) resides in the trachea, causing respiratory distress, coughing, and gasping [<a href="#ref-7">7</a>]. *Tetrameres* species infect the proventriculus, leading to glandular dysfunction [<a href="#ref-7">7</a>].

### Cestodes

Cestodes (tapeworms) require an intermediate host (e.g., beetles, flies, earthworms) for transmission. *Raillietina* species (*R. tetragona*, *R. cesticillus*, *R. echinobothrida*) and *Choanotaenia infundibulum* are common in the small intestine [<a href="#ref-1">1</a>, <a href="#ref-7">7</a>]. *Davainea proglottina* is a highly pathogenic cestode that causes severe enteritis [<a href="#ref-7">7</a>]. *Hymenolepis* species are also reported [<a href="#ref-7">7</a>].

### Trematodes

*Prosthogonimus* species (flukes) infect the oviduct and bursa of Fabricius, causing egg peritonitis and reduced egg production [<a href="#ref-1">1</a>]. Trematodes require a snail intermediate host for transmission.

## Protozoan Parasites

### Coccidia

*Eimeria* species are the most important protozoan [parasites of poultry](/knowledge/parasites/avian-parasites/parasites-poultry-chicken-eggs-meat), causing coccidiosis [<a href="#ref-9">9</a>, <a href="#ref-10">10</a>]. *[Eimeria tenella](/knowledge/parasites/avian-parasites/eimeria-tenella-chickens-cecal-coccidiosis-anticoccidial-resistance)*, *E. necatrix*, *E. acervulina*, *E. maxima*, and *E. brunetti* are the major pathogenic species [<a href="#ref-9">9</a>]. Coccidiosis is characterized by diarrhea, bloody droppings, reduced feed conversion, and mortality [<a href="#ref-10">10</a>]. *Cryptosporidium* species are also reported in poultry, with potential zoonotic implications [<a href="#ref-8">8</a>].

### Haemoparasites

*Plasmodium* species ([avian malaria](/knowledge/parasites/avian-parasites/avian-malaria-wild-captive-birds-vectors-diagnosis-conservation)), *Haemoproteus* species, and *Leucocytozoon* species are blood-borne protozoa transmitted by insect vectors [<a href="#ref-11">11</a>]. *Leucocytozoon caulleryi* is a significant pathogen in East and South Asia, causing anemia, leukopenia, and mortality [<a href="#ref-3">3</a>]. *Plasmodium gallinaceum* causes severe disease in chickens [<a href="#ref-11">11</a>].

### Flagellates

*[Histomonas meleagridis](/knowledge/parasites/avian-parasites/histomonas-meleagridis-turkeys-diagnosis-therapeutic-options)* causes histomonosis (blackhead), characterized by necrotic typhlitis and hepatitis [<a href="#ref-3">3</a>, <a href="#ref-8">8</a>]. *Tetratrichomonas gallinarum* is a related flagellate that causes enteritis [<a href="#ref-8">8</a>]. *Blastocystis* species are commonly detected in poultry but their pathogenic role is unclear [<a href="#ref-8">8</a>].

## [Chicken Parasites in Eggs](/knowledge/parasites/avian-parasites/parasites-poultry-eggs-risks)

Several parasites can be transmitted via the egg. *Ascaridia galli* eggs can be shed in feces and contaminate the eggshell surface [<a href="#ref-6">6</a>]. *Capillaria* eggs can be present in the egg contents if the oviduct is infected [<a href="#ref-8">8</a>]. *Eimeria* oocysts are not typically found in eggs but can contaminate the shell surface from fecal material [<a href="#ref-9">9</a>]. *Cryptosporidium* oocysts can be present on eggshells and pose a [zoonotic risk](/knowledge/parasites/pet-parasites/zoonotic-risk-humans-get-parasites-from-pets) [<a href="#ref-8">8</a>]. *Prosthogonimus* flukes directly infect the oviduct, leading to egg abnormalities and fluke eggs in the egg contents [<a href="#ref-1">1</a>].

## [Chicken Parasites in Meat](/knowledge/parasites/avian-parasites/parasites-poultry-chicken-eggs-meat)

[Parasites in poultry meat](/knowledge/parasites/avian-parasites/parasites-poultry-meat-public-health-veterinary-perspectives) are primarily a concern for [food safety](/knowledge/bacteria/livestock-bacteria/cooking-chicken-bacteria-prevention). *Ascaridia galli* and *Capillaria* species can cause carcass condemnation due to visible lesions [<a href="#ref-6">6</a>]. *Eimeria* species do not infect humans but cause economic losses due to reduced meat quality [<a href="#ref-9">9</a>]. *Cryptosporidium* species are zoonotic and can be transmitted via undercooked meat [<a href="#ref-8">8</a>]. *[Toxoplasma gondii](/knowledge/parasites/protozoa/toxoplasma-gondii-lifecycle-neurological-infection)* can be present in poultry meat and is a significant foodborne pathogen [<a href="#ref-12">12</a>].

## Diagnostic Approaches

Diagnosis of [poultry parasites](/knowledge/parasites/avian-parasites/parasites-in-poultry) relies on a combination of clinical examination, necropsy, and laboratory techniques.

### Fecal Examination

Fecal flotation (using saturated salt or sugar solutions) and sedimentation are standard methods for detecting nematode eggs and coccidian oocysts [<a href="#ref-7">7</a>, <a href="#ref-8">8</a>]. The McMaster counting chamber is used for quantitative egg counts [<a href="#ref-8">8</a>]. Modified Sloss technique is used for trematode eggs [<a href="#ref-7">7</a>].

### Necropsy

Direct visualization of adult worms in the intestine, ceca, and trachea is performed at necropsy [<a href="#ref-6">6</a>]. *Ascaridia galli* adults are 2-12 cm long, *[Heterakis gallinarum](/knowledge/parasites/avian-parasites/heterakis-gallinarum-cecal-worm-histomonas-vector)* are 0.5-1.5 cm, and *Capillaria* species are thread-like [<a href="#ref-6">6</a>].

### Molecular Diagnostics

PCR and qPCR are used for species-specific detection of *Eimeria*, *Histomonas*, *Cryptosporidium*, and *Blastocystis* [<a href="#ref-8">8</a>]. High-throughput sequencing can identify mixed infections [<a href="#ref-11">11</a>].

### Serology

ELISA for *Dermanyssus gallinae* antibodies is used for monitoring mite exposure [<a href="#ref-3">3</a>].

## Treatment and Control

### Anthelmintics

Fenbendazole is the only approved benzimidazole for poultry ascarids [<a href="#ref-6">6</a>]. Resistance has been reported in *Ascaridia galli* and *[Heterakis gallinarum](/knowledge/parasites/avian-parasites/heterakis-gallinarum-cecal-worm-histomonas-vector)* [<a href="#ref-6">6</a>]. Levamisole and piperazine are also used but have variable efficacy [<a href="#ref-6">6</a>]. Ivermectin is used off-label for ectoparasites [<a href="#ref-4">4</a>].

### Anticoccidials

Ionophores (monensin, salinomycin) and synthetic compounds (toltrazuril, diclazuril) are used in feed [<a href="#ref-9">9</a>]. Live vaccines using precocious or attenuated *Eimeria* strains are available [<a href="#ref-3">3</a>, <a href="#ref-9">9</a>].

### Ectoparasite Control

Pyrethroids, organophosphates, and carbamates are used for mite and lice control [<a href="#ref-4">4</a>]. Diatomaceous earth and sulfur dust are used in organic systems [<a href="#ref-4">4</a>].

### Biosecurity

Strict quarantine, cleaning, and disinfection are critical for preventing parasite introduction [<a href="#ref-8">8</a>]. Litter management and rotational grazing reduce environmental contamination [<a href="#ref-10">10</a>].

## Mermaid Diagram: Diagnostic Workflow for [Poultry Parasites](/knowledge/parasites/avian-parasites/poultry-parasites-and-diseases)

```mermaid
flowchart TD
 A["Clinical Signs: Diarrhea, Weight Loss, Anemia, Respiratory Distress"] --> B["Fecal Sample Collection"]
 B --> C["Fecal Flotation / Sedimentation"]
 C --> D{"Positive for Eggs or Oocysts?"}
 D -->|"Yes"| E["McMaster Count / Species ID"]
 D -->|"No"| F["Necropsy / Direct Visualization"]
 F --> G{"Adult Worms or Lesions?"}
 G -->|"Yes"| H["Species Identification / Morphology"]
 G -->|"No"| I["Molecular PCR / qPCR"]
 I --> J["Species Confirmation"]
 E --> K["Treatment Selection"]
 H --> K
 J --> K
 K --> L["Anthelmintic / Anticoccidial / Ectoparasiticide"]
 L --> M["Post-Treatment Fecal Exam"]
 M --> N{"Parasite Clearance?"}
 N -->|"Yes"| O["Biosecurity / Prevention"]
 N -->|"No"| P["Resistance Testing / Alternative Drug"]
 P --> K
```

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