Home › Animalia › Animal health › Animal diseases › Infectious necrotizing hepatitis
Infectious necrotizing hepatitis
Infectious necrotizing hepatitis, known to breeders as black disease, is a clostridiasis of the liver caused by Clostridium novyi. The spores of this bacteria are swallowed with the grass, pass into the blood and lodge silently in the liver...
What is it?
Infectious necrotizing hepatitis, known to breeders as black disease, is a clostridiasis of the liver caused by Clostridium novyi. The spores of this bacteria are swallowed with the grass, pass into the blood and lodge silently in the liver, where they can remain inactive for a long time without causing the slightest problem. Everything changes when something damages the liver and creates an area deprived of oxygen. In sheep, it is almost always the migration of young liver flukes which plays this role. The spores then wake up in the galleries dug by the moats, the bacteria multiplies and releases toxins which destroy the liver and kill the animal within a few hours. It is this link which makes all the practical interest of this disease: where there is fluke, there is a risk of black disease. Wetlands, pond edges, ditches and irrigated plots are therefore doubly dangerous. It mainly affects adult sheep in good condition, never the weakest: here again, it is the best animals that leave.
Key point
Sudden death of adults in excellent condition, in farms where liver fluke is present. Two measures and only two protect: clostridial vaccination and the fight against fluke. Never open an animal found dead yourself.
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:
In the vast majority of cases, the animal is simply found dead, often lying on its stomach, its head on its side, in excellent body condition.
When signs are observed, they rarely last more than a few hours: the animal stays behind the herd, isolates itself, no longer ruminates, refuses to eat.
Fever at first, then drop in temperature and cooling.
Rapid breathing, downed animal that no longer reacts to approach.
Mucous membranes pale, sometimes tinged with yellow.
The animal lies down and never gets up again, then dies.
Deaths often occur in series, a few days apart, in a herd grazing wetlands at the end of the dry season or after rains.
The name black disease comes from the very dark appearance that the skin of a corpse takes on when it is skinned.
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 spores of the bacteria are present in the soil, swallowed with grass, and attach to the livers of many perfectly healthy sheep. Their presence alone does not make you sick.
There needs to be a trigger that damages the liver and creates an oxygen-free zone: in sheep, it is the migration of young liver flukes in almost all cases.
Other liver damage can play the same role, more rarely: other parasites, various lesions.
In the gallery dug by the moat, the bacteria finds the conditions it needs to multiply. It then produces toxins which destroy liver tissue and pass into the blood.
Death is due to these toxins, not to the fluke itself: this is why the disease can strike an animal which did not appear sick from its fasciolosis.
Presence of liver fluke in the herd: this is the main triggering factor. A farm that has livers seized at the slaughterhouse is a high-risk farm.
Wet pastures: ponds, springs, ditches, lowlands, canals and irrigated plots.
Rainy seasons and years, periods following floods, end of dry season when animals concentrate on areas that remain green.
Adult sheep in good condition, often the heaviest in the herd.
Animals not vaccinated against clostridiosis.
Direct watering in ponds and ditches rather than from tanks.
Plots having already experienced cases in previous years.
Transmission
It is not a contagious disease: an affected sheep does not contaminate its peers or humans.
The spores come from the soil and are ingested with the grass. They persist for years in the plots.
When several animals die, it is not a contagion: it is because they all graze the same wetland and are subject to the same fluke pressure.
Marshy areas, the edges of ponds, ditches and irrigated plots are classic areas, because they bring together the small freshwater snail necessary for the fluke and a soil rich in spores.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian connects two elements: sudden deaths of adults in good condition, and a context of wetlands or known flukes on the farm.
The autopsy, carried out by the veterinarian, shows typical areas of destruction in the liver, often at the end of galleries dug by the flukes. It’s the exam that decides.
Never open a corpse yourself: anthrax gives the same picture of sudden death and presents a real danger to you and your family.
Liver samples may be sent to the laboratory to identify the bacteria.
The veterinarian will also take stock of the fluke: dropping analyzes, blood tests, returns of liver seizures to the slaughterhouse. This information conditions all future prevention.
Reports of livers seized at the slaughterhouse are a valuable source of alert, even when the animals appear in great shape.
Treatment
There is practically no treatment: the disease kills within a few hours and animals are almost always found dead.
On an animal detected very early, the veterinarian can try antibiotic and supportive treatment on prescription, with low chances of success.
All useful action concerns the herd: shelter the animals from wet areas without delay, and treat the fluke according to the strategy decided by the veterinarian.
Please note, active products against flukes are not interchangeable: some only act on adult forms installed in the canals, others also affect young migrating flukes, which are precisely those which trigger black disease. This choice is up to the veterinarian.
The usual wormers against roundworms have no action on the fluke: it is a frequent and costly confusion.
Waiting times for meat and milk are particularly long with products active against fluke and differ significantly from one product to another: ask for them before any treatment.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention is based on two inseparable pillars: vaccinating against clostridiosis and controlling fluke. One without the other leaves the problem unsolved.
Fence ponds, springs, the edges of ditches and shallows, especially during periods when infesting forms of fluke are most numerous on the grass.
Drain marshy areas when possible, repair leaking water troughs and pipes which create permanent puddles.
Water from the bin rather than from ponds and ditches.
Do not mow fodder in flood-prone areas to provide green fodder.
Monitor returns from the slaughterhouse: seized livers indicate fluke pressure, therefore a risk of black disease.
Reason treatments against fluke with the veterinarian according to the season and the analyzes, rather than on a fixed date.
Vaccinate the entire herd, including adults in good condition, who are most affected.
Vaccination
Multipurpose clostridial vaccines used in sheep farming generally cover this bacteria at the same time as other clostridiases.
In farms where the fluke is present, this vaccination is not an option: it is the only barrier when the young flukes migrate into the liver.
Protection is obtained by a primary vaccination in several injections followed by regular boosters. The schedule is set by the veterinarian, taking into account the risk periods linked to flukes in your area.
Unlike other clostridioses, it is the adults who must be protected as a priority, since they are the ones who die.
A vaccination given when the deaths begin does not catch up with the current episode: it must precede the risk period.
Respect the cold chain and do not keep an opened bottle from one campaign to the next.
Possible complications
Death of the animal, almost always without the possibility of intervention.
Serial losses over several weeks as long as the moat and access to wetlands are not controlled.
Losses concentrated on the heaviest and most productive animals in the herd.
Frequent association with the fluke's own damage: weight loss, anemia, drop in production, abortions.
Seizures of livers at the slaughterhouse and devalued carcasses.
When to see a veterinarian
An adult sheep in good condition is found dead without prior signs: call the veterinarian, do not open the corpse.
Several animals die within a few days of each other in a herd grazing wetlands.
The slaughterhouse informs you of seized livers: ask for advice even if your animals appear in great shape.
Animals slowly lose weight and graze on lowlands or irrigated plots.
An animal is slaughtered, no longer chews the cud, isolates itself from the herd: consult without delay.
Before the high-risk season, take stock of vaccinations and the fluke control plan with the veterinarian.
Prognosis
The individual prognosis is practically zero: the animals are found dead.
The herd's prognosis depends entirely on two things: vaccination and fluke control. Where both are in place, the disease disappears.
Where access to wetlands is not managed, losses return every year at the same period, despite treatment.
Frequently asked questions
What is the relationship between liver fluke and this disease?
A direct report. The young flukes dig galleries in the liver, and it is in these galleries that the bacteria, until then dormant, wakes up and produces its toxins. Without flukes, there is almost never black disease. This is why we cannot take care of one without taking care of the other.
Why are my most beautiful sheep dying?
Because it is adults in good condition who graze the most and harbor the most flukes. The disease does not strike weakened animals but those that are doing well, which makes it particularly discouraging for the breeder.
I am already treating against fluke, should I still vaccinate?
Yes. Fluke treatment reduces the pressure but does not guarantee that no young flukes will migrate into the liver, and not all products act on migrating forms. Clostridial vaccination is the only barrier at the critical moment.
Should we really fence the pond?
This is the most cost-effective measure of all. The fluke needs a small freshwater snail to complete its cycle: without access to wetlands, the chain breaks. Fencing and watering from the trough does more than any repeated treatment.
References
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
WOAH — Organisation mondiale de la santé animale (ex-OIE)
Content reviewed by the TunisieVet editorial team · Updated 11 August 2026
AT A GLANCE
Need a veterinarian?
Find a practitioner near you on TunisieVet, with their specialities, hours and contact details.
Find a veterinarianCategories
Affected species
This information is provided for educational purposes only and is not a substitute for a veterinary consultation. If you have any concerns about your animal's health, consult a veterinarian.
To discover
Related diseases and linked Animalia content.
Rabies
Viral · Vaccine available
Toxoplasmosis
Parasitic
Coccidiosis
Parasitic
Foot-and-mouth disease
Viral · Vaccine available