Coccidia in puppies – coccidiosis symptoms and treatment

Overview

Coccidia are microscopic, single-celled parasites, rather than intestinal worms. Common canine species are Cystoisospora canis and parasites in the C. ohioensis group.

Older test results and guidance may refer to them as Isospora. Infection can occur in a dog with diarrhoea or one with no symptoms at all.

In North American canine studies, positive findings have ranged from 3–38%. In Sweden, Cystoisospora oocysts are detected in around 3–7% of canine faecal samples sent to laboratories.

These are findings from different regions and differently selected dogs, rather than disease rates for puppies in other populations. Canine Cystoisospora species are host-specific and do not cause coccidiosis in people.

Causes

Oocysts mature into infective forms in the environment

Oocysts, the parasite's protected transmission stages, are shed in faeces and are not initially infective. An oocyst becomes infective as it matures, or sporulates, outside the dog.

Development to the infective stage usually takes a few days. In warm conditions at 30–37°C, maturation can occur in less than 16 hours.

A dog becomes infected by swallowing mature oocysts from a contaminated environment. Prey such as a mouse can also carry tissue stages of the dog's parasite and transmit infection when eaten.

This prey-borne route is less important than infection acquired from the environment. Dormant stages can remain infective in a prey animal's internal organs for several years.

Eating prey containing tissue stages can shorten the interval from infection to oocyst shedding.

Multiplication damages intestinal cells

The parasites multiply inside cells in the small and large intestine. Maturation of developmental stages and their exit from a cell destroy intestinal cells.

Parasite stages occur both in the surface cells of intestinal villi and in cells within the villi's inner tissue. C. canis can cause more severe intestinal damage than C. ohioensis.

The first oocysts usually appear in faeces 6–10 days after infection. Most animals shed oocysts for around 5–10 days.

Risk factors

The first infection is usually acquired while suckling, at around 3–8 weeks of age. However, symptomatic disease is most often diagnosed in puppies aged 2–4 months.

High animal density and accumulated environmental oocysts increase infection pressure in a breeding environment. Weaning, transport and moving to a new home can trigger infection-associated diarrhoea.

The transition to the first solid food may also contribute to diarrhoea in puppies. Another concurrent infection or a disease that weakens immunity can worsen coccidiosis.

Previous infection usually produces some immunity and reduces later symptoms. However, immunity to one Cystoisospora species does not guarantee protection from another species in the same genus.

C. canis oocysts are usually shed in large numbers only with the first infection. Reinfection with the C. ohioensis group, however, may appear in a faecal sample even when symptoms are milder than during the first infection.

Typical symptoms

Symptomatic coccidiosis is primarily an intestinal disease of young puppies.

• Stools become watery and may be yellow-green.

• Mucus or blood may be visible in diarrhoeic stools.

• Your puppy's appetite decreases and it does not eat as usual.

• Your puppy is subdued and tires more easily than usual.

• Weight falls or growth slows.

• Abdominal pain and vomiting may accompany the intestinal signs.

Profuse diarrhoea can rapidly cause dehydration needing treatment. Symptoms may begin when oocyst shedding starts or before the first detectable finding.

With reinfection, only small numbers of oocysts may be shed and the dog may remain symptom-free.

Complications and consequences

Severe diarrhoea can impair a puppy's fluid balance and nutritional status. Rarely, a severely affected puppy may die from coccidiosis.

However, most dogs with symptoms respond well to appropriately targeted treatment. Renewed exposure from contaminated surroundings can cause reinfection after treatment.

The problem may therefore continue in a breeding environment through subsequent litters. Dormant stages in tissues are generally not considered to cause clinical disease themselves.

Species developing in deeper intestinal cells can cause particularly severe cell damage.

Diagnosis at the vet

Faecal testing distinguishes canine parasites from organisms passing through

The vet considers the puppy's age, symptoms, background and faecal findings together. Oocysts are sought using centrifugal faecal flotation.

In the laboratory, oocyst size, structure and maturity help distinguish different coccidian genera. Closely related species within the C. ohioensis group are difficult to distinguish by appearance alone.

Flotation concentrates the parasite's transmission stages from a sample for microscopic examination. A symptomatic puppy may need a repeat sample if the first test is performed before oocyst shedding starts.

A positive oocyst finding alone does not establish that coccidia are causing the dog's symptoms. Cystoisospora antigen testing can complement microscopic faecal examination.

PCR can look for the parasite's genetic material in faeces. PCR may also be combined with microscopy where appropriate to use the strengths of both methods.

Eimeria oocysts may pass into a dog's faeces after it eats faeces from a rabbit, hare or ruminant, for example. Dogs are not the true hosts of Eimeria parasites, so this finding does not mean the dog has coccidiosis.

A severely ill puppy may also need blood tests to assess general condition and supportive-care needs. Other concurrent parasite infections must be considered because they may require separate treatment.

Treatment

Medication is selected according to symptoms and the infection situation

The vet decides whether coccidial treatment is needed according to symptoms and test results. A routine medicine for a puppy's intestinal worms is not necessarily effective against coccidia.

Toltrazuril and diclazuril are targeted medication options for coccidiosis. A sulfonamide may also be used at the vet's discretion.

Early treatment can reduce both diarrhoea in a litter and the number of oocysts shed into the environment. An affected puppy's littermates may already be infected before they start shedding oocysts themselves.

The veterinary treatment plan therefore also covers susceptible littermates and puppies in contact. In a breeding establishment with repeated disease, possible treatment of the dam is also assessed as part of infection control.

An adult dog without symptoms, however, does not usually need medication for a self-limiting infection.

Dehydration and nausea are treated alongside the infection

Treatment for a severely affected puppy may include fluid therapy. Separate medication may be needed to control vomiting and nausea.

A gastrointestinal diet may support recovery alongside medication. Supportive care also aims to prevent nutritional decline because a puppy with diarrhoea may receive insufficient nourishment.

Bathing the dog at the end of treatment removes faecal infectious material remaining in the coat. Environmental cleaning forms part of treatment because the dog can become reinfected from its surroundings.

Prevention

Complete elimination of coccidia from the environment is usually impossible, but infection pressure can be reduced. Remove faeces as soon as possible, before oocysts can mature into infective forms.

Dispose of faeces in a sealed bag with general waste. Do not put faeces in compost where the parasite's transmission stages are not adequately destroyed.

First remove visible dirt and faecal residue mechanically by washing or brushing. Mature oocysts withstand most ordinary disinfectants.

Steam cleaning is suitable for surfaces that tolerate it as part of coccidia control. Any disinfectant works best only once the surface is clean and dry.

Leave surfaces completely dry after washing, which reduces oocyst survival. Choose chemical treatment according to the surface's tolerance and the product's instructions.

Wash food and water bowls daily with hot water and use separate bowls for different pets. Wash bedding and other fabrics touching the dog at a minimum of 60°C if the material tolerates it.

Grass and bare soil cannot be disinfected in the same way as hard indoor surfaces. In a limited, heavily contaminated run, replacing topsoil or surface material may be an option.

In a moist, sheltered environment, oocysts can survive for up to 1 year if not exposed to freezing or extreme heat. However, ordinary frost cannot be relied on for control, as oocysts can also survive freezing.

Preventing prey-eating reduces one possible transmission route. Where possible, new dogs entering a breeding establishment are initially kept separate from others.

Reducing puppy stress around weaning and moving may help prevent diarrhoea developing. Smooth, washable kennel surfaces make regular cleaning easier.

Important for dog owners

Record your puppy's appetite, vomiting, stool quality and weight trend. Tell the vet whether littermates also have symptoms and when your puppy arrived home. Bring details of previous parasite treatments and the products used.

Do not take a puppy with diarrhoea to a dog park, and keep it separate from healthy animals.

Do not postpone investigation of severe puppy symptoms for weeks, even though mild diarrhoea in an adult dog may sometimes be monitored initially.

Samples may be requested from 3 bowel movements, each packed in its own tightly sealed bag.

Keep samples refrigerated before sending them, according to the laboratory's instructions.

Samples must be as fresh as possible to provide suitable material for testing.

Label the bag with the dog's and owner's names and the collection date so samples can be identified.

Seal the sample bags inside an outer bag as protection against leakage.

Samples waiting in the refrigerator must not freeze before delivery to the laboratory.

Agree on sample numbers, packaging and delivery with the treating practice. Also confirm how testing of littermates and cleaning at home should be timed alongside treatment. If your puppy becomes listless or vomiting increases, contact the veterinary team again.

Wash hands after handling animals and faeces so infectious material is not carried to other areas.

Frequently asked questions

Is coccidiosis the same as an intestinal worm infection?

Coccidia are single-celled protozoa, while intestinal worms belong to a different parasite group. A puppy's routine worming medicine may therefore not treat coccidiosis. Several concurrent parasites may also be responsible for symptoms and need their own treatments.

Can canine coccidiosis spread to people or cats?

Canine Cystoisospora species do not infect people or cats because they are host-specific. This applies specifically to Cystoisospora: some Giardia and Cryptosporidium strains, for example, can be shared by animals and people. Handwashing therefore remains part of faecal hygiene at home.

Why can the first faecal sample be negative?

Coccidiosis symptoms may begin before the dog sheds oocysts detectable in faeces. The vet may then need a repeat sample to investigate infection. Oocyst shedding usually starts 6–10 days after infection, so a very early sample may contain no detectable oocysts.

Does every positive dog need medication?

Infection in an adult dog without symptoms is often self-limiting and does not require medicine. Other susceptible puppies in an affected litter are a different situation because their infection may still be developing. The vet decides on medication needs according to symptoms and test findings.

Why does diarrhoea or infection return after treatment?

A dog can become reinfected from the environment if viable oocysts remain there. An ordinary disinfectant spray alone may not eliminate infective oocysts from surfaces. Removing visible dirt and allowing surfaces to dry completely therefore complement medication as control measures.