Heart Water | Sheep fever | Black dung Prevention and Cure

Heartwater (Hydropericardium):

Called “Black dung” when affecting African cattle and buffalo

“Sheep fever” when seen in sheep Heartwater is an acute, non contagious disease of cattle, sheep, goats, antelopes and wild ruminants. It is caused by the rickettsial organism Cowdria (Rickettsia) ruminantium.

black dung in a cow

1.Transmission:

Heartwater is transmitted by various species of Amblyomma ticks. Transstadial
transmission of the organism occur in vector ticks.

Antemortem findings :

Peracute form

1. Incubation 14–28 days
2. Fever
3. Diarrhoea
4. Convulsions and death
Acute form
5. Fever up to 41.7°C
6. Rapid breathing
7. Lack of appetite, depression and listlessness

Nervous signs include:

8. Twitching of the eyelids
9. Protrusion of the tongue
10. Champing of the jaw
11. Walking in circles
12. Paddling with legs in recumbent animals
13. Opisthotonos and convulsions

Postmortem findings:

1. Hydropericardium
2. Hydrothorax
3. Pulmonary edema and ascites
4. Haemorrhagic gastroenteritis
5. Enlarged liver, spleen and lymph nodes
6. Haemorrhage in the abomasum and intestine
7. Edema and haemorrhage of the brain

Judgement:

Carcass of an animal affected with heartwater is condemned in the acute stage of the disease. In a chronic case, the carcass may be approved if adequately bled and muscles are wholesome in colour and texture.

The affected organs are condemned.

2.Differential diagnosis:

Peracute form of heartwater should be differentiated from

anthrax

The acute nervous form of the disease is differentiated from

tetanus
rabies
cerebral
trypanosomiasis
strychnine poisoning
piroplasmosis
theileriosis
lead and organophosphate poisoning
parasitism
arsenical poisoning and poisoning with certain plants.

3.Treatment, Control, and Prevention:

Oxytetracycline at 10 mg/kg/day, IM, or doxycycline at 2 mg/kg/day will usually effect a cure if administered early in the course of heartwater infection.

A higher dosage of oxytetracycline (20 mg/kg) is usually required if treatment begins late during the febrile reaction or when clinical signs are evident. In such cases, the first treatment should preferably be given slowly IV. A minimum of three daily doses should be given regardless of temperature;

If fever persists, oxytetracycline treatment should continue for a fourth and fifth day. If the fever still does not abate, a potentiated sulfonamide at 15 mg/kg/day, IM, has been successful.

The withdrawal times for milk and meat after treatment with doxycycline, short- or long-acting oxytetracycline, and sulfonamides must be observed based on local regulations.

Corticosteroids have been used as supportive therapy (prednisolone 1 mg/kg, IM), although there is debate as to the effectiveness and rationale for their use.

Diazepam may be required to control convulsions.

Affected animals must be kept quiet in a cool area with soft bedding and be totally undisturbed; any stimulation can preempt a convulsive episode and subsequent death.

Vaccination can help with the control of heartwater; however, it is neither easily administered nor monitored and gives variable to no cross-protection to the various E ruminantium stocks.

Young calves (<4 week old), lambs, and kids (<1 week old) have an innate age-related resistance to heartwater, so if challenged by natural or induced infections within this time period, most recover spontaneously and develop a reasonable immunity.

Control of tick infestation is a useful preventive measure in some instances but may be difficult and expensive to maintain in others.

Excessive reduction of tick numbers, however, interferes with the maintenance of adequate immunity through regular field challenge in endemic areas and may periodically result in heavy losses.

Chemoprophylaxis involves a series of oxytetracycline injections to protect susceptible animals from contracting heartwater when introduced into endemic areas while also allowing them to develop a natural immunity.