Cryptosporidiosis
Cryptosporidiosis is the disease caused by the protozoan parasite Cryptosporidium. There are many species of Cryptosporidium but not all cause disease. The main species that causes disease in farm animals and humans is Cryptosporidium parvum.
Key facts
Why it matters
Cryptosporidiosis can cause serious disease outbreaks in susceptible animals, leading to animal health implications as well as financial losses to the farmers in both treatment costs and animal losses through death or reduced weight-gain.
The oocyst stage of the parasite can also survive many commonly used farm disinfectants and water chlorination treatment, making it difficult for farmers, vets and water suppliers to control or inactivate it.
Cryptosporidiosis is an illness caused by a tiny parasite called Cryptosporidium. The parasites are found in the intestines of infected animals and humans. In human outbreaks throughout the world, water is known to be the most common route of infection for Cryptosporidium, which is resistant to water chlorination. Humans are mainly infected with two species, C. parvum (which also infects animals) or C. hominis.
In the UK, drinking water is highly regulated so the numbers of outbreaks involving human illness from public water supplies has decreased significantly over the last 25 years with only three drinking water outbreaks between 2009 and 2023. As Cryptosporidium oocysts are widespread in the environment, they are frequently detected in water sources. Testing regimes by water companies will result in rapid interventions such as “notice to boil”.
It is important that the prevalence of this parasite is reduced as much as we possibly can in the interests of animal health and welfare, water quality and public health.
A feature of Cryptosporidium is its ability to multiply rapidly in the host leading to a potentially rapid spread of infection through a calf group or farm. The parasite achieves this as each oocyst hatches in the gut releasing four sporozoites which individually invade the gut wall, multiply and develop into oocysts, completing the life cycle in 2-7 days.
The damage to the gut caused by the invading and multiplying parasites leads to the clinical signs evident in animals infected with Cryptosporidium. In addition, during the infection process the parasite produces some thin-walled oocysts which burst open in the gut causing auto-infection within the host, leading to further multiplication of the parasite.
Transmission
animal-to-animal
Shed millions of oocysts in their faeces, durable in temperate, moist conditions which can be passed to other young animals.
Insects
Flies and insects can carry the parasite from one area to another.
Water
Drinking water in troughs, rivers and streams or used to prepare milk replacer can all be sources of infection.
Environmental
Oocysts survive for long periods once shed into the environment.
Other animals
Other livestock and wildlife can shed oocysts which are infective to young calves and lambs.
People
People handling animals can pass the parasite on between animals.
Contact with animals
Touching infected animals (i.e. young lambs or calves without washing hands afterwards.
Food
Eating unwashed fruit and vegetables, or food washed in contaminated water.
Directly from another person
Passed from one person to another, e.g. when changing a nappy and not washing your hands thoroughly.
Swimming in or drinking contaminated water.
Chlorination does not kill Cryptosporidium oocysts.
Clinical Signs
Initial signs
Profuse watery yellow diarrhoea with loss of appetite and lethargy.
Weight loss
Profuse diarrhoea and inappetence often leads to dehydration, fever and abdominal pain with weight-loss
Death
Depending on the severity and the strain of C. parvum severe cases can result in death
Long-term impact
Calves which had clinical cryptosporidiosis as newborns weighed less than calves on the same unit which did not have clinical cryptosporidiosis at six months of age.
Symptoms in humans include profuse watery diarrhoea, stomach pain, nausea and vomiting which can lead to dehydration and weight-loss. Symptoms usually last for a couple of weeks but in some cases can last longer and some people have life-long problems.
Diagnosis
What farmers might notice
You cannot diagnose cryptosporidiosis from clinical signs alone, as many other pathogens may cause diarrhoea in young calves. If you have scouring animals, you have some options.
Penside Test
Confirmation of clinical observation using faecal samples. Penside tests are available which can detect Cryptosporidium, E. coli K99, coronavirus and rotavirus.
Veterinary Test
SRUC Veterinary Services and the Animal and Plant Health Agency (APHA) offer calf enteritis screening packages which can include Cryptosporidium along with choices of combinations for the main bacterial and viral pathogens of calves. Your own veterinarian may also offer these services so check with them.
Post-mortem
Dead animals can be submitted for post-mortem examination. While this is too late for the calf in question, diagnosis of the pathogen(s) present will give you valuable information enabling you make informed management, treatment or preventative decisions for the other animals on your farm.
Identifying only the presence of the parasite by microscopy can be problematic for diagnosis as many Cryptosporidium species do not cause disease. There are few morphological differences between Cryptosporidium species and internal structures cannot be easily seen and it is not possible to speciate most species by microscopy alone.
The oocysts of Cryptosporidium are very small (3-8 µm), under microscopic examination Cryptosporidium oocysts can be difficult to distinguish from other small particles such as yeasts, moulds and faecal debris. Various techniques for detection of oocysts by microscopy exist.
The most common method used in UK diagnostic laboratories for human and veterinary specimens is modified Ziehl Neelsen (mZN). Using mZN the oocysts appear red on a blue/green background and the sensitivity of this method is ~75% with 100% specificity.
Prevention and Control
It is important to follow the manufacturer’s instructions for any product you use and to seek veterinary guidance if you are unsure and to confirm diagnosis.
Vaccination
In 2023 a new vaccine was licensed for protection of calves from C. parvum from birth. The vaccine (produced by MSD) is given to pregnant heifers and cows to produce colostrum containing protective antibodies. On consumption of the colostrum calves are protected from birth until two weeks of age.
Treatment
There are several products licensed for use against Cryptosporidium, but these all contain one of two active ingredients.
Halofuginone
Can be used as a preventative as well as a treatment. It reduces scouring and oocyst shedding but should not be administered to dehydrated/weak/anorexic calves and may be toxic if overdosed, therefore accurate calf weights are required. Must be used for 7 consecutive days.
Paromomycin
This is an antimicrobial (aminoglycoside) and as such must be prescribed by your vet where there is a definitive diagnosis of cryptosporidiosis. Paromomycin has been shown to reduce scour and shedding of oocysts. In is important to ensure you have accurate calf weights before dosing. Follow manufacturer’s instructions carefully and administer for between 5 and 7 consecutive days (product dependent).
Disinfectant
Many of the common farm disinfectants are NOT effective in killing Cryptosporidium oocysts when used at manufacturer’s recommended concentrations. Disinfectants which are effective against Cryptosporidium are shown and may be obtained through your vet or farm supplier. It is important to adhere to safety precautions provided with each chemical.
Effective Disinfectants
- 2-3% KENOTMCOX - kills 95% oocysts after 2 hours contact time
- 2-4% Neopredisan 135-1- kills 95% oocysts after 2 hours contact time
- 10% Ox-Virin - reduced oocyst infectivity after 1 hour contact time
- 3% Hydrogen Peroxide - reduced oocyst infectivity after 4 minutes
- 3.3.% K Swordsman® - kills 99.99% of oocysts after 12 hours contact time
Food safety
Wash and/or peel fruit, vegetables and salad before eating them, even if they state, “ready to eat”. If visiting a farm/petting zoo eat only in designated areas.
Reduce risk from animals
Always wash hands thoroughly using hot water and soap after working with, feeding or petting farm animals. You should pay special attention to hygiene during farm visits, washing hands after any contact with animals.
Water
Do not drink untreated water, do not consume ice or water in countries where the supply may not be safe. Avoid swallowing water in lakes, lochs, rivers or swimming pools.
Downloads & links
Related Resources
Video
Animation Series - Control the Crypto
Video
Centenary Film No. 6
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