A silent threat lurks in the most traditional of farming practices, affecting millions of birds worldwide.
For countless rural households, local breed chickens represent far more than livestock—they are living savings accounts, sources of daily nutrition, and embodiments of cultural heritage. In cities like Dhamar, Yemen, these birds scratch and peck their way through household courtyards and open markets, largely fending for themselves. Yet this traditional free-range system, while low-cost and natural, exposes chickens to invisible threats that compromise their health and productivity. Gastrointestinal parasites represent one of the most significant yet overlooked challenges to poultry health across the globe, particularly affecting local breeds managed in traditional systems.
The high prevalence of gastrointestinal parasites in local chickens isn't accidental—it's the direct result of their living conditions and management practices. Unlike commercially raised chickens kept in controlled environments, backyard poultry roam freely, exposing them to parasitic eggs and larvae in soil, feed, and water contaminated with droppings. These birds often become intermediate hosts through their consumption of infected insects, earthworms, snails, and slugs 1 7 .
Higher infection rates (82.6-84.8%) compared to cage systems (63.6%) 6
Research confirms that free-ranging and backyard systems show markedly higher infection rates (82.6-84.8%) compared to cage production systems (63.6%) 6 . The situation in Dhamar exemplifies this global pattern, where traditional rearing methods, while culturally embedded and economical, inadvertently create ideal conditions for parasitic transmission.
This large roundworm inhabits the small intestine, causing malnutrition, weight loss, and reduced egg production even in mild infections 7 . Global prevalence: 35.9% 6 .
While often causing minimal direct damage, it plays a more sinister role as a carrier of histomoniasis (blackhead disease) 3 .
Their feeding activity damages the mucosal lining, leading to inflammation, impaired nutrient absorption, and potentially fatal hemorrhages in severe cases 3 .
Tapeworms require intermediate hosts to complete their life cycles, making them particularly common in free-range systems.
Global prevalence: 19.0%. They attach to the intestinal wall, consuming nutrients and potentially causing intestinal blockages in heavy infections 1 6 .
Another common tapeworm species affecting free-range poultry 1 .
The causative agents of coccidiosis represent perhaps the most economically significant protozoan parasites in poultry. These organisms damage intestinal cells, leading to bloody diarrhea, dehydration, and high mortality, especially in young birds 3 .
Studies consistently show alarming prevalence rates, with one Colombian study reporting a 90% infection rate 3 .
| Parasite Type | Species | Global Prevalence | Primary Impact |
|---|---|---|---|
| Nematodes | Ascaridia galli | 35.9% | Nutrient deficiency, weight loss |
| Nematodes | Heterakis gallinarum | 28.5% | Vector for blackhead disease |
| Nematodes | Capillaria spp. | 5.9% | Mucosal damage, hemorrhage |
| Cestodes | Raillietina spp. | 19.0% | Intestinal blockage, malnutrition |
| Protozoa | Eimeria spp. | Varies by region | Diarrhea, dehydration, mortality |
Understanding parasite prevalence requires meticulous scientific investigation. The following methodology, drawn from similar studies conducted in comparable settings, illustrates how researchers assess the parasitic burden in chicken populations.
Researchers typically conduct cross-sectional surveys, randomly collecting fresh fecal samples from local chicken breeds. In a recent Gabon study, researchers gathered 402 fecal samples from semi-intensive poultry farms and free-range sites 8 . Samples are collected following a systematic pattern (often a "W" route through the coop) to ensure representative sampling, then refrigerated at 4°C until processing 9 .
Scientists primarily use two diagnostic techniques:
Researchers examine prepared slides under light microscopes, using 10× and 40× objectives. An ocular micrometer helps measure eggs' dimensions, allowing precise classification by genus and species based on morphological characteristics 9 .
The McMaster counting technique provides an estimate of infection intensity. Scientists dissolve a standardized fecal weight in flotation solution and count eggs or oocysts in specialized chambers, calculating eggs per gram (EPG) or oocysts per gram (OPG) of feces 9 . This quantitative approach helps distinguish between clinically insignificant infections and those likely causing disease.
| Parasite Type | Low Burden | Medium Burden | High Burden |
|---|---|---|---|
| Eimeria spp. | <1,800 OPG | 1,800-6,000 OPG | >6,000 OPG |
| Nematodes | <500 EPG | 500-2,000 EPG | >2,000 EPG |
Studies conducted in settings similar to Dhamar reveal consistent patterns. A Gabon study found 72.9% of chickens infected with gastrointestinal parasites, with Capillaria spp. (39.5%) and Ascaridia (31.1%) being most prevalent 8 . Alarmingly, mixed infections (60.7%) were more common than single infections, potentially compounding health impacts 8 .
Recent research from Central Chile detected Eimeria spp. in 72.5% of backyard poultry production systems, followed by Capillaria spp. (50.9%) and Ascaridia galli (49%) 9 . Importantly, most systems (nearly 90%) showed low parasitic burdens, suggesting that while exposure is widespread, clinical disease may be less common 9 .
| Item | Function | Application in Research |
|---|---|---|
| Saturated sodium chloride solution | Flotation medium | Concentrates parasite eggs by buoyancy |
| Microscope with calibrated ocular micrometer | Visualization and measurement | Identifies and measures eggs/oocysts |
| McMaster counting chambers | Egg quantification | Determines eggs/oocysts per gram of feces |
| Sample collection containers | Material transport | Maintains sample integrity from field to lab |
| Refrigeration unit | Sample preservation | Prevents degradation until processing |
Research consistently identifies specific protective factors that reduce parasitic prevalence:
Reduces fecal-oral transmission 9
Lowers humidity unfavorable to parasite survival 9
Removes parasitic eggs from environment 7
Reduces transmission density 7
Smallholder farmers across Africa have traditionally used plant-based remedies to control gastrointestinal parasites. The most commonly used plants include:
Farmers predominantly use leaves (47.62%), followed by bark and roots (11.9% each), preparing these as oral remedies 1 . While these traditional practices highlight indigenous knowledge, their efficacy requires further scientific validation.
The gastrointestinal parasites affecting local breed chickens in Dhamar and similar regions represent more than a veterinary concern—they impact household nutrition, economic resilience, and cultural practices. While traditional free-range systems offer numerous benefits, their parasitic challenges cannot be ignored.
Effective management requires integrating modern veterinary science with indigenous knowledge, developing context-appropriate strategies that respect traditional practices while safeguarding animal health. As research continues to illuminate the complex relationships between parasites, their hosts, and the environment, one truth remains evident: understanding these hidden hitchhikers is the first step toward protecting the chickens that countless households depend on.