Capillaria

Capillaria, commonly known as threadworms or hairworms, are slender nematode parasites that affect a wide range of bird species and represent one of the most pathogenic intestinal parasites in avian medicine. These parasites are named for their hair-thin appearance and can cause serious, even life-threatening disease, particularly in heavy infections or when affecting young or debilitated birds. Several species of Capillaria affect birds, with different species showing preferences for different locations within the gastrointestinal tract. Capillaria contorta primarily affects the crop and esophagus, Capillaria obsignata inhabits the small intestine, and Capillaria caudinflata affects the small intestine and ceca. Infections with these parasites are commonly termed capillariasis.

Capillaria transmission occurs through ingestion of embryonated eggs from the environment or, for some species, through consumption of earthworms that serve as intermediate hosts. The eggs develop into infective embryos in the environment over two to three weeks under suitable conditions. Once ingested by a susceptible bird, the eggs hatch and larvae develop into adult worms in the preferred location of the gastrointestinal tract. Adult Capillaria embed their anterior ends into the mucosal lining of the digestive tract, causing significant tissue damage and inflammation. The parasites feed on blood and tissue fluids, and heavy infections can cause severe pathology.

The impact of Capillaria infections on bird health can be devastating, particularly compared to some other intestinal parasites. The tissue-invasive nature of these worms causes more damage than parasites that simply reside in the intestinal lumen. Infections of the crop and esophagus interfere with normal food passage and can cause thickening and ulceration of these tissues. Intestinal infections disrupt nutrient absorption and can cause hemorrhage. Clinical signs often appear rapidly once infection becomes established, and progression to life-threatening disease can occur quickly without intervention. Capillariasis is considered a serious disease requiring prompt diagnosis and treatment.

Treatment of Capillaria infections is generally effective when initiated promptly, though this parasite can be more challenging to eliminate than some other intestinal worms due to its tissue-invasive habits. Effective anthelmintic medications are available, and supportive care helps birds recover from the damage caused by the parasites. However, prevention is preferable to treatment, and understanding the transmission routes allows implementation of effective control measures. Bird owners should work closely with avian veterinarians to diagnose, treat, and prevent Capillaria infections, particularly in species or situations known to be at high risk for these parasites.

The primary cause of Capillaria infection is ingestion of infective parasite eggs or intermediate hosts carrying larval stages. Capillaria eggs are shed in the droppings of infected birds and require a period of development in the environment before becoming infective. Under favorable conditions of warmth and moisture, embryonation occurs over approximately two to four weeks. Direct life cycle species infect new hosts when these embryonated eggs are ingested from contaminated food, water, or substrate. Some Capillaria species utilize earthworms as intermediate hosts, and birds become infected by consuming these worms. This indirect life cycle is particularly relevant for birds that forage on the ground and consume earthworms as part of their diet.

Environmental and husbandry factors significantly influence the risk of Capillaria infection. Moist environments favor survival and development of Capillaria eggs, which are susceptible to drying. Soil or natural substrate floors in aviaries provide ideal conditions for egg development and earthworm populations that may serve as intermediate hosts. Poor sanitation allowing fecal accumulation increases environmental egg loads. Overcrowded conditions concentrate parasites in smaller areas and increase stress, compromising immune function. Outdoor housing and access to areas frequented by wild birds increases exposure risk. Contaminated food and water sources serve as vehicles for egg transmission.

The life cycle of Capillaria contributes to its pathogenicity in bird hosts. After ingestion of embryonated eggs, larvae hatch and penetrate the mucosal lining of the targeted region of the digestive tract. The anterior portion of the adult worm remains embedded in the tissue, anchoring the parasite while it feeds on blood and tissue fluids. This tissue invasion causes mechanical damage, hemorrhage, and intense inflammatory responses. Female worms produce eggs that are shed in droppings, contaminating the environment and perpetuating the transmission cycle. The prepatent period, from infection to egg shedding, varies by species but typically ranges from three to five weeks.

Risk factors for Capillaria infection include housing conditions that favor parasite transmission, particularly dirt floors, moist environments, and access to areas where earthworms are present. Young birds are more susceptible to severe disease from Capillaria infections. Ground-feeding behavior increases exposure through contact with contaminated substrate or consumption of earthworm intermediate hosts. Multi-bird environments provide opportunities for transmission between birds. Introduction of infected birds to clean environments initiates contamination. Some bird species appear more susceptible to Capillaria than others, with gallinaceous birds, psittacines, and pigeons commonly affected.

The mechanism of disease causation by Capillaria involves direct tissue damage from the parasites themselves. The anterior end of the worm, embedded in the mucosal lining, causes mechanical destruction of tissue and disrupts normal epithelial function. Blood feeding results in hemorrhage and contributes to anemia in heavy infections. Inflammatory responses to the parasites cause thickening of the crop, esophagus, or intestinal wall, interfering with normal function. Secondary bacterial infections may develop at sites of tissue damage. Nutrient malabsorption from intestinal damage leads to malnutrition despite adequate food intake. The combined effects of tissue damage, blood loss, inflammation, and malnutrition can rapidly lead to deterioration and death in severe cases.

Early warning signs of Capillaria infection may be subtle initially but often progress rapidly as the parasites establish and cause tissue damage. Mild changes in appetite or eating behavior may be noticed, with birds showing hesitation while eating or apparent discomfort during swallowing if the crop or esophagus is affected. Slight weight loss or failure to maintain normal body condition can occur before more obvious symptoms develop. Decreased activity and subtle lethargy may be observed. Changes in dropping character, including looser consistency or altered color, can indicate intestinal involvement. Because these early signs are nonspecific, they may be attributed to other causes, delaying recognition of the parasitic infection.

As Capillaria infections progress, more characteristic symptoms develop. Weight loss becomes pronounced and may progress rapidly over days to a few weeks. Birds with crop or esophageal involvement may show difficulty swallowing, regurgitation, or crop distension from impaired motility. The crop may feel thickened or doughy on palpation. Appetite typically decreases significantly, though some birds may attempt to eat but have difficulty. Diarrhea is common with intestinal infections, and droppings may contain blood or appear dark due to digested blood from upper gastrointestinal hemorrhage. Overall condition deteriorates, with birds appearing weak and unwell.

Behavioral changes associated with Capillaria infection reflect the systemic impact of the disease. Affected birds become progressively lethargic, spending increasing amounts of time resting and showing little interest in normal activities. Reduced vocalization and social interaction are common. Birds may sit fluffed and huddled, a classic posture indicating illness. Reluctance to eat despite offering favorite foods is typical in moderate to severe infections. Sleep patterns may be disturbed. Young birds may fail to develop normally and show delayed acquisition of skills compared to healthy age-matched individuals.

Physical signs of Capillaria infection include progressive weight loss with prominent keel bone and muscle wasting. Feather condition deteriorates, with plumage appearing dull, ruffled, and unkempt. Pale coloration of the cere, skin, and mucous membranes indicates anemia from blood loss. Droppings may be loose, contain mucus, or show evidence of blood. The vent area may become soiled from diarrhea. In birds with crop involvement, the crop region may appear distended or feel abnormal on palpation. Overall, the bird appears unthrifty and in poor condition despite previously being healthy.

Symptom progression in Capillaria infections can be alarmingly rapid. Unlike some parasitic infections that develop gradually over weeks to months, capillariasis can cause rapid deterioration over just one to two weeks once clinical signs appear. Initial mild symptoms quickly intensify as parasite numbers increase and tissue damage accumulates. Anemia from blood loss compounds the effects of malnutrition from impaired digestion. Secondary infections may develop at sites of tissue damage, adding to the disease burden. Without treatment, severely affected birds may die within days of showing obvious symptoms.

Emergency symptoms requiring immediate avian veterinary care include severe weakness, inability to perch, or collapse. Complete refusal to eat for more than 24 hours in a bird showing other symptoms warrants urgent attention. Bloody droppings or signs of significant hemorrhage indicate serious disease. Extreme lethargy, cold feet, and rapid or labored breathing suggest shock and require emergency intervention. Severe weight loss with a very prominent keel bone indicates advanced disease requiring intensive care. Young birds with Capillaria infections can deteriorate extremely rapidly and should be considered emergencies when symptoms are present. Any bird suspected of having Capillaria should be seen by an avian veterinarian promptly due to the potential for rapid progression.

Diagnosis of Capillaria infection begins with a thorough history and physical examination by an avian veterinarian. The history should include details about the bird's housing, diet, exposure to soil or earthworms, and contact with other birds. Physical examination findings in capillariasis often include poor body condition, prominent keel bone, ruffled feathers, and pale mucous membranes indicating anemia. Palpation of the crop may reveal thickening or abnormal texture in birds with upper digestive tract involvement. The veterinarian will assess overall condition and look for signs of secondary complications. The combination of compatible history, clinical signs, and physical findings raises suspicion for Capillaria infection.

Fecal examination is the primary diagnostic method for confirming Capillaria infection. Fecal flotation techniques concentrate parasite eggs for microscopic identification. Capillaria eggs have a distinctive appearance, being barrel-shaped or football-shaped with polar plugs at each end. This characteristic morphology allows differentiation from other parasite eggs. However, egg shedding may be intermittent, particularly early in infection, and a single negative fecal examination does not rule out capillariasis. Multiple samples collected over several days increase diagnostic sensitivity. In some cases, eggs may be demonstrated in crop washings if the parasites are present in the upper digestive tract.

Additional diagnostic tests help assess the severity of disease and detect complications. Complete blood count often reveals anemia, which may be severe in heavy infections, along with eosinophilia and other inflammatory changes. Blood chemistry panels evaluate organ function and identify metabolic derangements from malnutrition or dehydration. Crop cytology may reveal inflammatory cells and sometimes parasite eggs in birds with crop involvement. Radiographs may show thickened crop walls or other abnormalities. In deceased birds, necropsy with careful examination of the gastrointestinal tract provides definitive diagnosis, with adult worms visible as thin, thread-like structures embedded in the mucosal surface.

Differential diagnosis for Capillaria infection includes other conditions causing weight loss, anemia, and gastrointestinal symptoms. Other intestinal parasites such as ascarids, coccidia, and giardia produce overlapping clinical signs. Bacterial or fungal crop infections cause similar symptoms when the crop is involved. Candidiasis of the crop causes thickening and regurgitation. Proventricular dilatation disease affects appetite and causes wasting. Megabacteria causes chronic weight loss. Systemic diseases affecting digestion or causing anemia must be considered. Accurate diagnosis relies on fecal examination findings combined with clinical presentation. Because Capillaria can cause rapid deterioration, treatment may be initiated based on strong clinical suspicion while awaiting or repeating diagnostic tests.

Emergency and immediate treatment for birds severely affected by Capillaria focuses on stabilization before or alongside antiparasitic therapy. Birds presenting in critical condition require aggressive supportive care including intravenous or subcutaneous fluid therapy to combat dehydration and support circulation. Supplemental heat is essential for hypothermic birds. Nutritional support through tube feeding provides calories and nutrients for birds too weak to eat. Blood transfusions may be necessary in cases of severe anemia, though this is logistically challenging in avian patients. Once the bird is stabilized, antiparasitic treatment is initiated. In less severe cases, treatment can begin immediately upon diagnosis with supportive care provided concurrently as needed.

Medical management of Capillaria infections requires effective anthelmintic medications administered at appropriate doses for sufficient duration. Fenbendazole is commonly used and effective against Capillaria, typically administered orally once daily for three to seven consecutive days depending on severity. Levamisole provides an alternative treatment option and may be given orally or by injection. Ivermectin is sometimes used, though it may be less effective against Capillaria than some other parasites and requires careful dosing in small birds. Combination treatments or repeated courses may be necessary for heavy infections or resistant cases. The veterinarian selects appropriate medications and doses based on the bird species, severity of infection, and any concurrent health issues.

Surgical intervention is rarely required for Capillaria infections themselves, but may be necessary to address complications. Severe crop impaction from dysfunction caused by parasitic damage may occasionally require surgical intervention. Secondary abscesses or necrotic tissue may need debridement. In most cases, medical management alone is sufficient, with supportive care addressing the consequences of parasitic damage while anthelmintic medications eliminate the worms.

Supportive care is critical for recovery from Capillaria infections given the significant tissue damage these parasites cause. Nutritional support through easily digestible, nutrient-dense foods helps restore body condition. Tube feeding may be necessary for birds unable or unwilling to eat independently. Iron supplementation may be indicated for anemic birds to support red blood cell regeneration. Probiotics help restore normal intestinal flora. Maintaining appropriate warmth and humidity supports recovery. Minimizing stress through quiet housing and gentle handling allows the bird to direct energy toward healing. Medications to protect the gastrointestinal lining may be prescribed to promote healing of damaged tissues.

Environmental treatment is essential to prevent reinfection and eliminate sources of ongoing contamination. All enclosures must be thoroughly cleaned, with complete removal of substrate material that may harbor eggs. Solid floors that can be disinfected are preferable during and after treatment. Earthworm access must be eliminated if these serve as intermediate hosts. Repeated cleaning over several weeks addresses newly hatched larvae and eggs not killed by initial cleaning. Other birds in the environment should be tested and treated as appropriate. Complete environmental decontamination combined with effective bird treatment prevents the cycle of reinfection that can occur when only the bird is treated.

Treatment decisions balance multiple factors including disease severity, bird species, and practical considerations. Capillaria infections require prompt, aggressive treatment due to their potential for rapid progression and serious consequences. More intensive treatment protocols may be warranted compared to less pathogenic parasites. Cost considerations include medications, supportive care, follow-up testing, and potential hospitalization for severe cases. Expected outcomes depend heavily on the severity of infection at the time of diagnosis and treatment initiation. Birds diagnosed and treated early generally have good prognoses, while those with advanced disease and significant complications may have prolonged recovery or guarded outcomes. Follow-up fecal examinations confirm treatment success.

The recovery timeline for birds treated for Capillaria infections depends on the severity of tissue damage and overall health status at diagnosis. Birds with early or mild infections may show improvement within the first week of treatment and recover fully within two to three weeks. More severely affected birds with significant weight loss, anemia, or tissue damage may require four to eight weeks or longer for complete recovery. The healing of damaged crop, esophageal, or intestinal tissue takes time even after the parasites are eliminated. Initial improvement in energy and appetite is typically seen within the first week as the parasite burden decreases, but full restoration of weight and condition requires sustained nutritional support.

Post-treatment care requirements include completion of the full prescribed course of antiparasitic medication even if the bird appears improved before treatment ends. Follow-up fecal examinations should be performed approximately two to three weeks after treatment completion to confirm elimination of the parasites. Continued nutritional support with high-quality, easily digestible foods promotes tissue healing and weight restoration. Activity may need to be limited during early recovery for severely debilitated birds. Environmental cleaning must be maintained to prevent reinfection from persistent eggs in the environment. Additional treatments for secondary conditions such as anemia or secondary infections continue as prescribed.

Prognosis factors for birds recovering from Capillaria infections include the extent of tissue damage at diagnosis, the bird's age and baseline health, response to treatment, and success of environmental decontamination. Birds diagnosed and treated early before severe tissue damage occurs have excellent prognoses. Those with advanced disease, severe anemia, or complications have more guarded prognoses, though many still recover with intensive care. Young birds may be more vulnerable to severe disease but also have greater regenerative capacity if they survive the acute phase. Quality of life during recovery is supported by appropriate nutrition, comfortable housing, and gradual return to normal activities as strength improves.

Long-term outlook following successful treatment of Capillaria infection is generally good for birds that recover from the acute disease. Once the parasites are eliminated and tissue healing is complete, birds typically return to normal health. Some birds with severe crop or esophageal damage may have persistent dysfunction, though this is uncommon with appropriate treatment. Reinfection is possible if exposure to contaminated environments continues, making ongoing prevention essential. Regular fecal monitoring helps detect any recurrence early. With proper prevention measures including environmental management and avoiding exposure to intermediate hosts, most birds maintain good health long-term after recovering from capillariasis.

Environmental prevention is fundamental to controlling Capillaria in bird populations. Maintaining clean, dry housing reduces the moist conditions that favor parasite egg survival and development. Regular removal of droppings prevents accumulation of eggs in the environment. Solid flooring that can be thoroughly cleaned and disinfected is preferable to natural substrates where eggs persist. Preventing access to soil and earthworms is particularly important for species susceptible to Capillaria species that use earthworms as intermediate hosts. Elevated feeding and watering stations reduce contamination of food and water with droppings. Regular rotation of enclosure areas, when possible, allows natural reduction of environmental parasite loads through drying and ultraviolet exposure.

Quarantine protocols prevent introduction of Capillaria to established collections. All new birds should be quarantined separately for a minimum of 30 to 45 days, with fecal examinations performed during this period to detect parasitic infections. Multiple fecal tests increase the likelihood of detecting infections that may shed eggs intermittently. Prophylactic deworming of new arrivals may be considered, particularly for birds from high-risk sources. The quarantine area must be completely separate from other birds with no shared equipment. Birds should have multiple negative fecal examinations before introduction to the main collection. Thorough cleaning between quarantine occupants prevents transmission from one bird to the next.

Dietary prevention supports immune function and overall health. A complete, balanced diet provides nutrients needed for optimal immune response to parasitic challenges. Vitamin A supports healthy epithelial tissues that resist parasite invasion. Adequate protein is essential for tissue repair and immune function. Avoiding earthworms and other potential intermediate hosts in the diet eliminates this transmission route for susceptible Capillaria species. Some bird owners choose to avoid offering live insects that forage in soil to minimize risk. While good nutrition cannot prevent infection, well-nourished birds are better equipped to respond to treatment and recover fully.

Health maintenance through regular avian veterinary care facilitates early detection of Capillaria infections. Routine wellness examinations allow assessment of overall condition and discussion of parasite risks based on the bird's specific situation. Regular fecal screening, at least annually and more frequently for high-risk birds, detects infections before clinical signs develop. Early treatment of light infections prevents progression to severe disease and limits environmental contamination. For facilities with known Capillaria problems, strategic prophylactic treatment protocols may be recommended by the veterinarian.

Early intervention when Capillaria is suspected is critical given the potential for rapid disease progression. Bird owners should become familiar with early warning signs including subtle weight loss, changes in appetite, and altered droppings. Any suspicion of Capillaria warrants prompt veterinary evaluation given the serious nature of this parasite. When infection is diagnosed in one bird, all potentially exposed birds should be tested. Immediate environmental decontamination limits ongoing transmission. Working proactively with an avian veterinarian to assess risk factors and implement appropriate prevention measures provides the best protection against this serious parasitic infection.

Daily management for birds recovering from or at risk for Capillaria requires consistent attention to hygiene and monitoring. Daily cleaning of enclosures removes droppings before eggs have time to develop to infectious stages. Food and water dishes should be cleaned daily to prevent contamination. Observing the bird's appetite, activity level, and dropping character helps detect any deterioration or signs of reinfection. Weight monitoring, ideally performed weekly, provides objective assessment of recovery progress or early warning of problems. Medication administration must follow the prescribed schedule exactly to ensure treatment effectiveness. Maintaining detailed records of treatments, weights, and observations provides valuable information for veterinary consultations.

Home environment modifications support treatment success and ongoing prevention. Enclosures should be set up to facilitate thorough daily cleaning, with smooth surfaces and removable perches and accessories. Substrate should be easily replaced and should not retain moisture that favors egg development. For birds that previously had access to soil or outdoor areas where earthworms are present, these exposures should be eliminated during and after recovery. Temperature and humidity should be maintained at appropriate levels for the species while avoiding the moist conditions that support parasite survival. Creating a clean, well-managed environment is one of the most effective ways to prevent Capillaria reinfection.

Maintaining quality of life during Capillaria management requires balancing strict hygiene with the bird's behavioral needs. While environmental restrictions may be necessary, especially during recovery, providing appropriate enrichment maintains mental health. Foraging opportunities using clean food sources keep birds mentally engaged. Social interaction with owners continues to meet social needs. As birds recover, gradually expanding their environment and activities supports both physical and psychological wellbeing. Avoiding excessive stress from overly restrictive management helps maintain immune function. The goal is to provide a clean, safe environment without completely eliminating the environmental complexity that birds need for mental health.

Ongoing monitoring and care become routine for birds that have experienced Capillaria infections. Regular fecal examinations, typically every three to six months, confirm continued absence of parasites and provide early warning of any reinfection. Weight monitoring detects subtle changes that might indicate emerging problems. Annual wellness examinations allow professional assessment and updating of prevention protocols as needed. Maintaining awareness of potential exposure sources helps avoid reinfection. Promptly addressing any symptoms that might suggest parasitic infection prevents progression to serious disease.

Caregiver support helps bird owners manage the challenges of Capillaria prevention and treatment. Understanding that this parasite can cause serious disease emphasizes the importance of prevention and prompt treatment. Avian veterinarians provide guidance on prevention strategies appropriate for individual situations. Bird clubs and online communities offer opportunities to learn from others' experiences. Educational resources about avian parasites help owners understand the risks and prevention options. Planning for potential veterinary costs reduces stress when care is needed. With proper management, Capillaria infections are preventable, and birds that have been treated can live normal, healthy lives with appropriate ongoing care.

Birds at highest risk for Capillaria infections include those with housing or behavioral factors that increase exposure to infective eggs or intermediate hosts. Gallinaceous birds including chickens, turkeys, pheasants, and quail are commonly affected, with Capillaria being a significant problem in poultry production and game bird facilities. Pigeons and doves are frequently infected with Capillaria species adapted to these hosts. Ground-dwelling birds and those housed on natural substrates with access to soil face elevated risk. Birds that consume earthworms, either intentionally offered or incidentally ingested during foraging, risk infection with Capillaria species using these intermediate hosts. Wild-caught or wild-rescued birds often harbor Capillaria infections from their natural environments.

Psittacines and other commonly kept pet birds can be affected by Capillaria when exposed to contaminated environments. Finches, canaries, and other small birds kept in outdoor aviaries or on natural substrates encounter Capillaria eggs in their environments. Lories and lorikeets may be exposed through soft foods that can become contaminated. Larger psittacines including cockatiels, conures, amazons, african greys, cockatoos, and macaws housed in facilities with soil access or where earthworms are present face infection risk. Young birds of any species are more susceptible to severe disease from Capillaria infections due to developing immune systems and greater sensitivity to the effects of malnutrition and blood loss.

Screening recommendations for Capillaria depend on the bird's risk factors. High-risk birds including ground-dwelling species, those with access to soil or earthworms, and birds in multi-bird facilities should have fecal examinations performed every three to six months. All new birds entering a collection should be tested during quarantine, with multiple fecal samples evaluated to account for intermittent egg shedding. Annual fecal screening is recommended for indoor pet birds with lower exposure risk. Any bird showing symptoms compatible with capillariasis should be tested promptly regardless of routine screening schedules. Given the potential for rapid disease progression, a low threshold for testing suspicious cases is appropriate. Working with an avian veterinarian to develop screening protocols based on individual risk assessment provides optimal protection against this serious parasitic infection.

Conditions commonly co-occurring with Capillaria infections include other gastrointestinal parasites, as environments supporting these parasites often harbor multiple species. Ascarids, coccidia, and tapeworms may be present simultaneously, requiring comprehensive fecal examination and potentially combination treatments. Malnutrition frequently accompanies Capillaria infections due to blood loss and impaired nutrient absorption. Secondary bacterial infections may develop at sites of tissue damage caused by the embedded parasites, particularly in the crop or intestinal mucosa. Anemia from blood loss is common with significant Capillaria burdens and may require supportive treatment beyond antiparasitic medications. Immunosuppression from chronic parasitism and malnutrition increases susceptibility to other opportunistic infections.

Conditions with symptoms similar to Capillaria infection require differentiation through appropriate diagnostic testing. Other intestinal parasites cause overlapping symptoms of weight loss, poor condition, and altered droppings. Candidiasis of the crop causes regurgitation, weight loss, and crop dysfunction similar to Capillaria contorta infections. Bacterial crop infections produce comparable upper digestive tract symptoms. Proventricular dilatation disease causes weight loss, regurgitation, and wasting. Megabacteria causes chronic weight loss and digestive disturbances. Nutritional deficiencies produce poor condition and feather quality. Accurate diagnosis through fecal examination and other appropriate tests ensures correct treatment is provided. Given the potential severity of Capillaria, prompt testing is warranted when this parasite is suspected.

Potential complications of Capillaria infection include severe anemia from blood loss that may be life-threatening, particularly in small birds or those with heavy burdens. Secondary bacterial infections at sites of tissue damage can lead to localized abscesses or systemic sepsis. Chronic damage to the crop or esophagus may result in persistent dysfunction even after parasites are eliminated. Intestinal damage can lead to malabsorption syndromes. Severe malnutrition affects multiple organ systems and delays recovery. In young birds, growth retardation and developmental delays may have lasting effects. Prevention of complications relies on early detection through routine screening, prompt treatment of identified infections, and aggressive supportive care for severely affected birds. Complete environmental decontamination prevents reinfection that could compound tissue damage.