Roundworms

Roundworms are the most common intestinal parasites found in dogs worldwide, affecting puppies with particularly high frequency due to efficient maternal transmission routes. These large, spaghetti-like worms belong to the ascarid family, with Toxocara canis being the primary species affecting dogs and Toxascaris leonina occurring less frequently. Adult roundworms can grow to several inches in length and live free in the small intestine, where they feed on the partially digested intestinal contents rather than attaching to the intestinal wall. The prevalence of roundworm infection in puppies is remarkably high, with studies suggesting that the majority of puppies are born infected or become infected shortly after birth through their mother's milk.

The life cycle of canine roundworms is complex and involves both migration through body tissues and environmental contamination. Adult female roundworms in the intestine produce enormous numbers of eggs, with a single female capable of producing hundreds of thousands of eggs daily. These eggs pass out in the feces and, under appropriate environmental conditions, develop into infective larvae within the egg shell over several weeks. Dogs become infected by ingesting these embryonated eggs from contaminated soil, grass, or objects. Puppies most commonly acquire infection before birth through transplacental transmission of larvae from the mother's tissues, or after birth through transmammary transmission in the mother's milk. This maternal transmission explains why deworming protocols begin at such young ages.

Roundworm infection impacts canine health through several mechanisms including nutritional competition, intestinal irritation, and potential physical obstruction. The worms compete with the host for nutrients, which can be particularly significant in young, growing puppies with high nutritional demands. Heavy worm burdens cause intestinal inflammation and may interfere with normal nutrient absorption. In severe cases, particularly in young puppies, large numbers of worms can form a physical mass that obstructs the intestinal tract, creating a medical emergency. The larval migration phase, during which ingested larvae travel through the liver and lungs before returning to the intestine, can cause coughing and respiratory symptoms and may predispose to secondary pneumonia.

Treatment of roundworm infection is straightforward and highly effective with readily available deworming medications. Multiple anthelmintic drugs are effective against adult roundworms, with most treatments requiring administration over several days or as repeated doses to ensure complete elimination. The excellent response to treatment and the availability of effective medications make roundworm infection a very manageable condition despite its high prevalence. However, the zoonotic potential of Toxocara canis, meaning its ability to infect humans and cause disease, makes prevention and treatment particularly important from a public health perspective. Veterinary guidance ensures appropriate deworming protocols, particularly for puppies and pregnant dogs where transmission risk is highest.

The primary cause of roundworm infection in dogs is exposure to the parasitic nematode Toxocara canis or, less commonly, Toxascaris leonina. Dogs acquire these parasites through several transmission routes, with the route of infection influencing how the larvae behave in the body. Ingestion of embryonated eggs from contaminated soil, grass, or other environmental surfaces represents a common infection route, particularly for dogs that explore and mouth objects during outdoor activities. Dogs may also become infected by eating intermediate hosts such as rodents that harbor encysted larvae in their tissues. For the majority of puppies, however, infection occurs through direct transmission from their mother either before or shortly after birth.

While roundworm susceptibility is not genetically determined, the circumstances of birth and early life create inherent risk for puppies born to infected mothers. Transplacental transmission occurs when encysted larvae residing dormant in the mother's tissues are reactivated during pregnancy and migrate across the placenta to infect developing puppies in utero. This means puppies can be born already carrying roundworm larvae in their tissues. Transmammary transmission provides another efficient route, with larvae passing into the mother's milk and infecting nursing puppies during their first weeks of life. These maternal transmission routes result in nearly universal infection rates among puppies born to undewormed mothers and explain why puppy deworming protocols are so critical.

Environmental and lifestyle factors significantly influence roundworm exposure risk beyond maternal transmission. Roundworm eggs are remarkably resilient and can survive in soil for years under favorable conditions, making environmental contamination a persistent problem. Dogs with outdoor access, particularly those that spend time in areas frequented by other dogs such as parks, yards, and public spaces, face ongoing exposure risk. Puppies that explore by mouthing objects and putting their noses to the ground have high exposure potential. Dogs that hunt or scavenge may ingest infected rodents or other prey animals carrying encysted larvae. Geographic location matters, as roundworm prevalence varies by region, climate, and local dog population density.

Multiple risk factors increase the likelihood and potential severity of roundworm infection. Age is the most significant factor, with puppies experiencing both higher infection rates due to maternal transmission and more severe clinical disease due to their small size and developing immune systems. Dogs in crowded housing situations such as shelters, breeding facilities, and pet stores face increased environmental exposure. Poor sanitation and inadequate waste removal allow environmental egg accumulation. Dogs with compromised immune systems may develop more severe infections and have difficulty controlling parasite numbers. Previous infection provides partial immunity in adult dogs but does not prevent reinfection entirely, and this immunity does not develop until dogs are several months old.

The mechanism of roundworm infection involves a fascinating migration pattern that varies depending on the route of infection and the age of the host. When a dog ingests embryonated eggs, the larvae hatch in the intestine, penetrate the intestinal wall, and travel through the bloodstream to the liver and then the lungs. In young puppies, the larvae continue their migration by traveling up the airways, being coughed up and swallowed, and then maturing into adult worms in the small intestine. In older dogs with developed immunity, this hepatotracheal migration is largely blocked, and larvae instead become encysted in various tissues including muscles, liver, and kidneys. These encysted larvae can remain dormant for the life of the dog but become reactivated during pregnancy, completing the transmission cycle to the next generation.

Early warning signs of roundworm infection may be quite subtle, particularly in adult dogs with low to moderate parasite burdens. Initial symptoms often include mild digestive changes such as occasional soft stools or changes in stool consistency that owners might attribute to dietary factors. Some dogs develop mild intermittent vomiting that may not seem significant. A slightly distended or pot-bellied appearance, particularly after eating, may be noted in puppies with developing infections. Mild decreases in energy or slight changes in appetite might occur but are easily overlooked. In puppies, the earliest sign may be a failure to gain weight at the expected rate compared to littermates or breed standards, requiring careful monitoring to detect.

The most characteristic symptom of significant roundworm infection, particularly in puppies, is the development of a pot-bellied or distended appearance. This abdominal distension results from intestinal irritation, gas accumulation, and the physical presence of worms within the intestinal tract. Heavy infections cause visible changes in stool quality, with affected dogs producing loose, mucoid, or foul-smelling feces. In some cases, particularly with severe infections or following certain deworming treatments, adult worms may be visible in the vomit or stool, appearing as long, whitish, spaghetti-like strands that can be quite alarming for owners to discover. Vomiting becomes more frequent and may contain visible worms or mucus.

Behavioral changes associated with roundworm infection reflect the dog's gastrointestinal discomfort and nutritional deficits. Infected dogs, particularly puppies, may display decreased energy and reduced enthusiasm for play. Changes in appetite are common, ranging from increased hunger due to nutritional competition from worms to decreased appetite from intestinal discomfort. Some dogs develop pica, eating non-food items such as dirt or grass, potentially in response to nutritional deficiencies or abdominal discomfort. Affected puppies may appear less playful than their littermates and may sleep more. Irritability or discomfort when the abdomen is touched might indicate intestinal cramping or discomfort.

Physical signs of roundworm infection extend beyond the characteristic pot-bellied appearance. Poor growth and failure to thrive are hallmark signs in puppies with significant infections, who may appear thin except for their distended bellies. The coat often becomes dull, dry, and rough in texture due to nutrient malabsorption. Weight loss or poor weight gain occurs despite adequate food intake because worms consume significant portions of the nutritional content. In heavy infections, anemia may develop, causing pale gums, though this is less pronounced than with blood-feeding parasites like hookworms. Coughing may occur during the larval migration phase when larvae travel through the lungs, and this respiratory involvement can be mistaken for kennel cough or other respiratory infections.

Symptom progression depends on infection intensity, the dog's age, and immune status. In adult dogs with functioning immunity, infections often remain subclinical or cause only mild intermittent symptoms. These dogs serve as reservoirs for environmental contamination while appearing relatively healthy. In puppies, symptoms typically progress from mild digestive upset to more obvious signs of poor growth and abdominal distension over several weeks. Without treatment, heavily infected puppies become increasingly malnourished and may develop secondary complications. The worm burden tends to increase over time as more larvae complete their migration and mature into egg-producing adults, accelerating environmental contamination.

Emergency symptoms requiring immediate veterinary attention, while relatively uncommon, can occur with severe roundworm infections. Intestinal obstruction occurs when a large mass of worms blocks the intestinal tract, causing severe abdominal pain, persistent vomiting, inability to defecate, and progressive deterioration. Signs of obstruction include a severely distended abdomen, unproductive retching, and extreme lethargy or collapse. Rarely, migrating worms may obstruct the bile duct or be vomited up and potentially aspirated into the airways. Puppies showing signs of severe debilitation, including extreme weakness, dehydration, or collapse, require emergency care. Any puppy that suddenly deteriorates after an apparently healthy period should be evaluated promptly for complications of parasitic infection.

The diagnostic process for roundworm infection begins with a clinical examination and detailed history taking by the veterinarian. During the physical examination, the veterinarian assesses the dog's overall body condition, paying particular attention to abdominal contour and evidence of the characteristic pot-bellied appearance. Body weight and growth trajectory are evaluated, especially in puppies where failure to thrive may indicate significant parasitic burden. The coat quality and overall condition provide clues about nutritional status and potential chronic infection. The veterinarian will ask about the dog's age, origin, deworming history, and any observed symptoms such as vomiting, diarrhea, visible worms, or changes in appetite and behavior.

Definitive diagnosis of roundworm infection relies on laboratory identification of the characteristic eggs through fecal examination. Standard fecal flotation tests process a stool sample to concentrate parasite eggs for microscopic examination. Roundworm eggs are distinctive, with Toxocara canis eggs appearing spherical with a thick, pitted outer shell, while Toxascaris leonina eggs are more oval with a smooth shell. A negative fecal test does not always rule out infection, as eggs may not be present if only immature worms or migrating larvae are present, or if the sample does not contain eggs despite infection. In puppies where roundworm infection is strongly suspected based on clinical signs, treatment may be initiated without fecal confirmation given the high probability of infection.

Differential diagnosis considers other conditions that may produce similar symptoms in dogs. Other intestinal parasites including hookworms, whipworms, tapeworms, and protozoal infections can cause gastrointestinal symptoms and should be identified or ruled out through comprehensive fecal testing. Dietary indiscretion or food intolerance may cause vomiting and diarrhea similar to parasitic infection. Inflammatory bowel disease produces chronic digestive symptoms in some dogs. Exocrine pancreatic insufficiency causes poor growth and digestive disturbance. Intestinal foreign bodies may cause obstruction with symptoms similar to severe roundworm impaction. Infectious diseases such as parvovirus cause severe gastrointestinal illness in puppies and must be distinguished from parasitic infection.

Once roundworm infection is confirmed or strongly suspected, the veterinarian assesses the severity to guide treatment and monitoring recommendations. The estimated worm burden, based on egg counts and clinical signs, influences treatment intensity and follow-up testing schedules. Overall health status, including hydration, nutritional condition, and any concurrent health issues, affects supportive care recommendations. Age is particularly important, as young puppies require more intensive monitoring and may need additional nutritional support. Household composition, including the presence of other pets and young children, influences recommendations for environmental management given the zoonotic potential of Toxocara canis. Results from fecal flotation are typically available the same day when performed in-house, allowing prompt initiation of treatment.

Initial treatment for roundworm infection focuses on eliminating adult worms from the intestinal tract while providing any necessary supportive care. For most dogs with uncomplicated infections, treatment can be managed entirely on an outpatient basis with oral deworming medications and home care instructions. Dogs with severe infections, significant dehydration, or signs of intestinal obstruction may require more intensive initial treatment including fluid therapy and careful monitoring. In rare cases of complete intestinal obstruction from a worm mass, emergency intervention including possible surgical removal may be necessary, though this complication is uncommon when infections are identified and treated before reaching such severity.

The mainstay of roundworm treatment is anthelmintic medication that paralyzes or kills adult worms in the intestinal tract. Several effective medications are available, including pyrantel pamoate, fenbendazole, milbemycin oxime, and others. Pyrantel pamoate is particularly commonly used for puppies due to its excellent safety profile and effectiveness. Fenbendazole provides broad-spectrum activity against multiple parasite types and is often given for three to five consecutive days. The choice of medication depends on the dog's age, weight, concurrent infections with other parasites, and any breed-related medication sensitivities. Treatment must typically be repeated in two to three weeks to eliminate worms that have matured from larvae since the initial treatment, as most dewormers only kill adult worms.

Surgical intervention for roundworm infection is rarely required and reserved for the uncommon complication of intestinal obstruction from massive worm burdens. When obstruction occurs, initial management attempts conservative treatment with fluids, gastrointestinal support, and deworming medication in hopes that the worm mass will break up and pass. If conservative management fails or the dog deteriorates, surgical exploration and removal of the obstructing worm mass may be necessary. This is most likely to occur in very young puppies with overwhelming infections who have not received timely deworming. The vast majority of roundworm infections resolve completely with medical treatment alone.

Supportive care complements deworming treatment and helps dogs recover from the nutritional and physical effects of infection. A highly digestible, nutrient-dense diet supports catch-up growth in puppies whose development has been impacted by infection. Small, frequent meals may be better tolerated initially than larger meals, particularly in dogs with gastrointestinal irritation. Ensuring adequate hydration is important, especially for dogs that have experienced vomiting or diarrhea. Probiotic supplements may help restore healthy intestinal flora. For puppies with significant growth deficits, ongoing nutritional support and monitoring help ensure they reach their genetic potential.

Complementary approaches focus on environmental management to prevent reinfection and reduce public health risk. Prompt removal of all feces from the environment limits egg contamination and development. Though roundworm eggs require several weeks to become infective, environmental egg loads can accumulate to high levels in untreated situations. Hard surfaces can be cleaned with dilute bleach, though eggs are resistant to many common disinfectants. Soil contamination is difficult to eliminate, as eggs can persist for years in appropriate conditions. Limiting access to heavily contaminated areas, such as kennels or yards where large numbers of dogs have defecated, reduces reinfection risk. Teaching children about hand hygiene after playing in potentially contaminated areas addresses the zoonotic health concern.

Treatment decisions are influenced by practical considerations including the dog's age, household circumstances, and concurrent conditions. For puppies, treatment typically follows established protocols beginning at two weeks of age with repeated doses every two weeks until at least eight weeks of age, then monthly until six months of age. Adult dogs may require less intensive initial treatment but benefit from regular ongoing prevention. Multi-dog households benefit from simultaneous treatment of all dogs to prevent cross-infection. Pregnant dogs require carefully timed treatment with pregnancy-safe medications to reduce transmission to puppies. The presence of young children in the household increases the importance of thorough treatment and environmental management. With appropriate treatment, prognosis for roundworm infection is excellent.

Recovery from roundworm infection typically proceeds smoothly once appropriate deworming treatment is administered. Owners often notice improvement in their dog's symptoms within days of starting treatment, with decreased vomiting and normalization of stool consistency among the early signs of response. Adult worms may be visible in the stool for several days after treatment as they are expelled from the intestinal tract, which, while potentially alarming, indicates effective treatment. Abdominal distension gradually resolves over one to two weeks as intestinal inflammation subsides and gas production normalizes. Appetite typically improves quickly, and increased energy becomes apparent within the first week of treatment.

Post-treatment care focuses on completing the full deworming protocol, supporting nutritional recovery, and preventing reinfection. Deworming medication must be repeated according to the prescribed schedule, typically at two to three week intervals, to eliminate worms maturing from larvae that were not killed by the initial treatment. A high-quality diet supports recovery and catch-up growth in puppies whose development was affected by infection. Continued vigilance about fecal removal from the environment prevents recontamination. Follow-up fecal examinations two to four weeks after completing treatment confirm successful elimination of adult worms. For puppies, ongoing deworming at regular intervals continues through six months of age and transitions to a regular preventive program thereafter.

Prognosis for dogs with roundworm infection is excellent with appropriate treatment. The vast majority of infected dogs experience complete resolution of symptoms and return to normal health within weeks of starting treatment. Puppies typically show rapid catch-up growth once the parasitic burden is eliminated and nutritional absorption normalizes. Adult dogs with mild infections may show minimal change if symptoms were subtle, but they benefit from reduced environmental contamination and elimination of zoonotic risk. Even dogs with heavy infections generally respond well to treatment when intervention occurs before the rare complication of intestinal obstruction develops. The main factor affecting prognosis is the timing of treatment, with earlier intervention producing better outcomes.

The long-term outlook for dogs following roundworm treatment is positive with appropriate ongoing prevention. Dogs that have been successfully treated experience no lasting effects from the infection and achieve normal health and development. However, immunity to roundworms is only partial, and dogs remain susceptible to reinfection throughout their lives, making regular preventive treatment essential. Monthly preventive medications that include activity against roundworms provide reliable ongoing protection. Annual fecal examinations help detect any breakthrough infections early. For previously infected puppies, ongoing monitoring of growth ensures they are catching up to normal development. With consistent preventive care, dogs can maintain roundworm-free status indefinitely.

Primary prevention of roundworm infection centers on regular deworming protocols that interrupt the parasite's life cycle before clinical disease develops. Puppies should receive their first deworming treatment at two weeks of age, with treatment repeated every two weeks until eight weeks of age, then monthly until six months of age. This aggressive early treatment addresses the near-universal infection rate in puppies due to maternal transmission. After six months, dogs should transition to regular preventive medication, typically monthly products that protect against multiple parasites including roundworms. Many heartworm preventive medications also provide roundworm protection, simplifying the preventive regimen for owners.

Responsible breeding practices significantly reduce roundworm transmission from mother to puppies. Pregnant dogs should be dewormed during the last trimester of pregnancy using veterinary-approved medications that are safe for use during gestation. This treatment reduces the number of encysted larvae available for transplacental migration, resulting in lighter infections in puppies at birth. Nursing mothers should continue deworming during lactation to reduce transmammary transmission. Maintaining breeding dogs on regular preventive protocols minimizes their overall parasite burden. Whelping areas should be kept scrupulously clean, with immediate removal of all fecal material to prevent environmental contamination.

Nutritional factors support immune function and help dogs resist the effects of roundworm infection. A complete and balanced diet meeting all nutritional requirements supports optimal immune system development and function. Puppies particularly benefit from high-quality nutrition during their rapid growth phase, helping them resist parasitic challenges. Maintaining appropriate body condition optimizes immune responses. While good nutrition cannot prevent infection, well-nourished dogs typically experience less severe disease when infected and recover more quickly following treatment.

Regular veterinary care provides the foundation for effective roundworm prevention through monitoring and professional guidance. Annual fecal examinations should be part of routine preventive care for all adult dogs, detecting infections before they cause significant disease or environmental contamination. Puppies should have fecal examinations at each vaccination visit during their puppy series. Dogs adopted from shelters, rescues, or breeding facilities should be tested and dewormed promptly upon acquisition. Discussion with the veterinarian about local parasite prevalence and individual risk factors helps determine the most appropriate preventive protocol for each dog.

Early intervention and environmental management complement pharmaceutical prevention. Prompt removal of feces from yards and outdoor spaces prevents egg development and accumulation in the environment. Teaching children to wash hands after playing outdoors, particularly in areas frequented by dogs, addresses zoonotic transmission risk. Discouraging dogs from eating prey animals that may harbor encysted larvae reduces one transmission route. Avoiding highly contaminated areas such as untreated kennels or dog runs with heavy fecal burden limits exposure. Working with veterinary staff to establish and maintain appropriate preventive programs provides the best protection against roundworm infection and its potential complications.

Daily management during active roundworm treatment requires attention to medication administration, hygiene practices, and monitoring for improvement. Deworming medication should be given exactly as prescribed, typically with food to improve absorption and reduce the possibility of stomach upset. Owners should monitor for expected passage of worms in the stool, which is normal following treatment and indicates effectiveness. Any vomiting of worms should be reported to the veterinarian but is generally not concerning unless persistent. Fecal material should be removed from the environment immediately, and hands should be washed thoroughly after handling feces or cleaning up accidents. Children should be supervised to ensure they do not contact potentially contaminated areas.

Home environmental management helps prevent reinfection and protects family members from zoonotic exposure. Yards should be kept clear of fecal material through daily removal, and heavily contaminated areas should be avoided until natural egg die-off occurs over time. Hard surfaces can be cleaned with dilute bleach or other appropriate disinfectants. Sandboxes and play areas should be covered when not in use to prevent contamination. Indoor accidents should be cleaned thoroughly with appropriate cleaners. Regular washing of dog bedding in hot water helps maintain a clean environment. In multi-dog households, all dogs should be treated simultaneously to prevent cross-infection.

Maintaining quality of life during treatment is straightforward since most dogs feel noticeably better within days of starting medication. Activity levels can remain normal unless the dog shows signs of significant illness requiring rest. Appetite typically improves quickly, and owners can encourage eating by offering palatable, digestible foods. Social interactions and normal routines can continue throughout treatment, as roundworm transmission occurs through fecal contamination rather than direct contact. Puppies should continue their socialization activities and training during treatment. Monitoring weight gain in puppies helps track recovery and catch-up growth.

Ongoing monitoring ensures treatment success and maintains parasite-free status. Owners should observe for complete resolution of symptoms including normalization of stool quality, resolution of abdominal distension, and improved appetite and energy. Follow-up fecal examinations confirm elimination of infection and should be performed as recommended by the veterinarian. Any return of symptoms should prompt veterinary evaluation for possible reinfection or other causes. Regular preventive medication should be administered consistently to prevent future infections. Annual fecal testing as part of routine veterinary care provides ongoing surveillance.

Caring for a dog with roundworm infection involves minimal special challenges for most owners, as treatment is straightforward and effective. The main concerns involve protecting children and other household members from potential zoonotic exposure through good hygiene practices. The cost of treatment is generally modest, though multiple rounds of deworming and follow-up testing add up. Understanding that roundworm infection is extremely common, especially in puppies, helps owners maintain perspective and focus on appropriate treatment and prevention rather than feeling concerned about their pet's condition. Working with veterinary staff ensures appropriate treatment protocols and preventive strategies tailored to individual circumstances.

Roundworm infection does not demonstrate significant breed predisposition and affects dogs of all breeds, sizes, and genetic backgrounds with similar frequency when exposure occurs. The near-universal maternal transmission route means that puppies of all breeds face equivalent risk of infection from their mothers regardless of breed-specific factors. However, certain breed-related circumstances may influence infection rates or detection. Breeds commonly produced in high-volume breeding operations may have higher infection rates at the time of sale due to environmental conditions, though this reflects husbandry practices rather than genetic susceptibility. Working and sporting breeds with significant outdoor exposure face ongoing environmental transmission risk.

Some breed categories warrant consideration in the context of roundworm treatment selection. Herding breeds, particularly Collies, Shetland Sheepdogs, and related breeds, may carry the MDR1 gene mutation causing sensitivity to certain medications including some antiparasitic products, requiring careful product selection and potentially genetic testing before certain treatments. Very small and toy breed puppies may require precise dosing calculations to ensure appropriate medication administration. Giant breed puppies, with their rapid growth rates, may be particularly affected by the nutritional competition from heavy worm burdens. Breeds with compromised immune function due to genetic factors may have more difficulty controlling infection naturally.

Screening and prevention recommendations apply equally across all breeds. All puppies should begin deworming at two weeks of age regardless of breed, following standard protocols through six months of age. Adult dogs of all breeds benefit from annual fecal examinations and regular preventive treatment. Breeding dogs of all breeds should be tested and treated appropriately before breeding and during pregnancy. Dogs newly acquired from any source should be tested and treated promptly. Working with a veterinarian to establish appropriate prevention protocols based on individual lifestyle factors rather than breed alone provides the most effective protection against roundworm infection.

Several conditions commonly occur alongside roundworm infection in dogs, reflecting shared risk factors and transmission environments. Concurrent infection with other intestinal parasites is extremely common, particularly in puppies from environments with inadequate parasite control. Hookworms frequently occur alongside roundworms due to similar maternal transmission routes and environmental exposure. Coccidia, a protozoal parasite, often affects the same young dog populations susceptible to roundworms. Giardia may be present concurrently, creating complex parasitic burdens. Tapeworm infection may occur in dogs with flea exposure or those that hunt prey. Comprehensive fecal testing helps identify all parasites present so appropriate combination treatment can be administered.

Numerous conditions produce symptoms similar to roundworm infection, making accurate diagnosis important for appropriate treatment. Other intestinal parasites cause overlapping symptoms of diarrhea, poor growth, and digestive upset. Parvovirus infection causes severe gastrointestinal illness in puppies that must be differentiated from parasitic disease. Dietary intolerance or food allergy produces chronic digestive symptoms similar to parasitic infection. Inflammatory bowel disease causes ongoing gastrointestinal disturbance. Exocrine pancreatic insufficiency results in poor growth and maldigestion. Intestinal foreign body ingestion may cause vomiting and abdominal distension. These conditions require different treatments, emphasizing the importance of proper diagnostic evaluation.

Complications of roundworm infection, while uncommon with appropriate treatment, can occur in heavily infected or untreated dogs. Intestinal obstruction from a mass of worms represents the most serious complication, requiring emergency intervention. Secondary bacterial pneumonia may develop when larval migration through the lungs creates opportunity for bacterial infection. Nutritional deficiencies affecting growth and development occur with chronic heavy infections. Biliary obstruction may rarely occur if worms migrate into the bile ducts. In humans, particularly children, the zoonotic infection visceral larva migrans can cause significant disease when Toxocara larvae migrate through body tissues, emphasizing the public health importance of treating and preventing canine roundworm infection.