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Giardiasis
Giardiasis is caused by a microscopic parasite which attaches to the wall of the small intestine of young ruminants, without destroying it but hindering the absorption of food. It mainly affects lambs and kids from a few weeks of life until...
What is it?
Giardiasis is caused by a microscopic parasite which attaches to the wall of the small intestine of young ruminants, without destroying it but hindering the absorption of food. It mainly affects lambs and kids from a few weeks of life until a few months, often around weaning. Its usual face is not spectacular diarrhea, but loose stools that come and go, with animals eating but not growing as they should. It is a disease of underperformance: it costs kilos and days of growth rather than deaths. Many breeders carry it without knowing it. It rarely circulates alone: in young people, it frequently accompanies coccidia, cryptosporidiosis and digestive worms, which complicates interpretation and requires a serious diagnosis.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Soft or pasty stools, sometimes frankly liquid, often clear, frothy and smelly, without blood.
A very characteristic sawtooth progression: the droppings return to normal for a few days, then soften again, and this lasts for weeks.
Hindquarters and tail wool intermittently soiled.
Stalling growth: animals of the same age and from the same batch begin to clearly distinguish themselves from each other.
Animals that eat properly but do not take on the expected condition, dull wool or hair, less lively general appearance.
Decreased appetite and depression in the most affected animals, especially at the time of weaning.
Weight loss in young people strongly affected.
Many carrier animals show absolutely nothing: they eliminate the parasite and maintain the contamination without becoming ill.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The parasite lives attached to the wall of the small intestine and disrupts digestion and the absorption of fats and sugars: the food passes through without being properly used.
It is eliminated in droppings in a form of microscopic resistance, immediately infective to another animal.
Young people become contaminated by swallowing these forms: soiled litter, stagnant water, dirty buckets and troughs, dirty udders, licked walls and barriers.
The quantity necessary to contaminate an animal is small, while affected animals eliminate a lot: contamination sets in very quickly in a grouped batch.
Resistance forms survive well in humidity and cold, but do not tolerate complete drying and full sun.
Elimination is irregular: the same animal can emit a lot one day and almost none the next, which complicates the diagnosis.
Adults often carry the parasite without being sick and serve as a reservoir for the young.
Lambs and kids from a few weeks to a few months, especially around weaning.
Grouping of many young people in a small space.
Damp litter, poorly drained buildings, permanently soiled corners.
Drinking from dirty buckets, puddles or stagnant water sources.
Weaning stress, sudden dietary changes, transportation.
Coexistence with other digestive parasites, which aggravates poor performance.
Unbalanced or insufficient ration: the loss of absorption is then paid for twice.
Reuse of the same premises without cleaning or drying between two belts.
Transmission
Transmission through the digestive tract: anything soiled with droppings can contaminate: litter, water, troughs, equipment, hands and boots.
Water is an important vector: dirty drinking troughs, puddles, points of stagnant water trampled by animals.
There is no transmission through the air or through simple proximity: it is always ingestion that is the cause.
Adult carrier animals without signs contaminate young ones, particularly at the time of giving birth and breastfeeding.
Transmission to humans is possible, even if most human cases have other origins: the usual hygiene precautions in breeding therefore remain justified.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The diagnosis is not made by eye: soft stools in a young ruminant have many possible causes, parasitic, microbial or dietary.
The veterinarian has fresh droppings analyzed. The search for this parasite requires a particular technique, different from the classic search for worm eggs: this must be specified in the laboratory.
As elimination is irregular, a negative examination is not enough to rule out the disease: the veterinarian may request repeated samples over several days or from several animals in the batch.
Finding this parasite does not automatically mean that it is the cause of everything: many healthy animals carry it. It is the comparison between the analysis, the state of the animals and the growth curves that allows us to conclude.
The veterinarian systematically looks for other associated causes, in particular coccidia in animals of the same age and digestive worms in those that graze.
Regular weighing of batches is the best monitoring tool: it shows the dropout and, later, the effect of the measures taken.
Treatment
Internal antiparasitics exist and act on this parasite, but they are not used like an ordinary dewormer: the administration schedule is specific and is entirely up to the veterinarian's decision.
No dose or duration should be decided alone, and you should not just give the usual wormer from the farm hoping that it will be enough.
Treatment alone never solves the problem: without sanitation of the premises and the water, the animals become recontaminated immediately and soft stools return a few weeks later.
At the same time as the treatment, troughs and drinkers must be cleaned, litter changed, wet areas dried and the density reduced in the room.
Animals that have a lot of loose stools need clean water at all times, a good quality, easy to digest ration, and a dry environment.
Meat and milk waiting periods apply depending on the products used and must be requested from the veterinarian before any slaughter or milking.
When several parasites are present at the same time, the veterinarian prioritizes: treating a single agent when another dominates gives no visible results.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Keep the young on dry and abundant litter, clean the soiled corners, avoid areas that remain permanently damp.
Clean drinkers and troughs regularly: consistently clean water is one of the most effective measures.
Remove access to puddles and stagnant water points that have been trampled.
Reduce the density of groups of young people and avoid mixing animals of very different ages.
Clean, disinfect and above all allow the premises to dry completely between two strips: drying is particularly effective on the resistance forms of this parasite.
Take care of the weaning period: gradual dietary transitions, no sudden changes, avoid combining weaning, transport and change of premises on the same day.
Ensure a balanced ration: an intestine that absorbs less well needs quality food.
Weigh young batches regularly to spot growth stalling early.
Wash hands after handling animals and clean boots and equipment between batches.
Possible complications
Growth delay that cannot be fully recovered, with animals emerging later and lighter.
Durable heterogeneity of batches of young people, difficult to correct afterwards.
Weakening which favors other diseases of young age, notably digestive and respiratory.
Dehydration when diarrhea becomes severe in younger children.
Recurring problem from one band to another when premises and water are not sanitized.
When to see a veterinarian
Young people have loose stools that come and go for several weeks.
Lambs or kids from the same batch begin to be clearly distinguished by size and condition.
Growth stalls even though the ration and food have not changed.
Soft stools persist after a classic dewormer: you must look for another cause rather than repeating the same product.
A young animal becomes depressed, refuses to eat or becomes dehydrated: consult without delay.
The problem comes back to each flock, at the same stage: you have to review all housing, water and weaning with the veterinarian.
Transmission to humans
This parasite exists in several variants. Those circulating in sheep and goats are mainly variants adapted to ruminants, and the risk of human contamination from the herd is considered limited. Variants capable of infecting humans can, however, be found in farm animals: caution therefore remains necessary.
In humans, the infection causes diarrhea, which is often prolonged, with bloating, cramps, nausea and fatigue. It can be treated, but can last several weeks if it is not taken care of.
Contamination always occurs through the digestive tract: soiled hands brought to the mouth, untreated water, poorly washed food. In humans, untreated drinking water is a much more frequent source of contamination than contact with a herd.
The precautions are the same as for all digestive diseases in livestock: washing hands with soap and water after working with animals and before any meal, no eating or drinking in buildings, clothing and boots reserved for breeding, potable or treated family drinking water.
In the event of prolonged diarrhea in the family, consult a doctor and report the breeding activity to him: this information helps guide the examinations. Do not take treatment on your own.
Prognosis
The vital prognosis is good: this disease rarely kills, except in very young animals already weakened by other causes.
The economic prognosis is more severe: the growth delay among young people cannot be completely recovered.
Animals treated and returned to a clean, dry environment recover well, but become recontaminated quickly if the premises and water remain contaminated.
At the herd level, control is based on housing hygiene, water quality and weaning management, more than on medications.
Frequently asked questions
My lambs have soft droppings at times, without being really sick: is this serious?
This is the typical presentation of this disease, and it is a signal that should not be ignored. It rarely kills but is costly in lost growth. A suitable dropping analysis, requested from the veterinarian, allows you to know if this parasite is the cause and if it is alone.
I dewormed and it didn't change anything, why?
Because the usual wormers are used against worms, in a pattern which is not the one required here. This parasite requires a special approach decided by the veterinarian, and above all sanitation of the premises and the water: without this, the animals become immediately recontaminated.
Can I catch this disease from my sheep?
The variants circulating in sheep and goats are mainly adapted to ruminants, and the risk from a herd is considered limited, without being zero. In humans, contamination comes much more often from untreated water. The usual precautions are sufficient: washing hands with soap and water, no eating in buildings, drinking water.
The analysis came back negative even though my lambs are doing poorly: is it reliable?
A single negative test is not enough here, because the parasite is eliminated irregularly from one day to the next. The veterinarian may request repeated samples, or from several animals in the batch, and will at the same time look for other possible causes of poor growth.
References
CDC — Centers for Disease Control and Prevention
ESCCAP — European Scientific Counsel Companion Animal Parasites
Content reviewed by the TunisieVet editorial team · Updated 11 August 2026
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