Volg ons op Facebook

Terrible Ticks

Written by  Dr. Joan Kleynhans
| in Veearts
| April 7, 2015

I remember a medical friend once telling me that he did not want to get a dog for his children because he was concerned that they might catch disease from it. My reply was that I have contracted many more diseases from humans than from animals in spite of decades of close contact with the latter. His children got their dog.

However, it is a fact that those of us who have close contact with farm and domestic animals, are at risk of catching certain diseases from them. Diseases that are transmitted from animals to humans are called zoonoses. In some cases the causative organism may cause very mild, imperceptible infection in the animal, but potentially fatal illness in the human.
One such disease is Crimean Congo haemorrhagic fever (CCHF). It is caused by a tick-borne virus, Nairovirus of the Bunyaviridae family. CCHF is endemic to Africa, the Balkans, the Middle East and Asian countries south of the 50th parallel north, depending on where the transmitting tick occurs. Animals become infected when they are bitten by an infected tick. The virus remains in their bloodstream for about a week after infection. When another tick bites them during this period, the tick acquires the virus and can transmit it to the next host. A number of tick genera are capable of becoming infected with the virus, but ticks of the genus Hyalomma (bontpoot-bosluis) are the principal vectors.
A wide range of animals can become infected, such as cattle, sheep and goats, as well as ostriches. An outbreak in humans has been reported at an ostrich abattoir in Oudtshoorn.  Many wild birds are resistant to infection.  Infected animals show no apparent disease.
Humans may become infected if they are bitten by infected ticks or if they come into contact with blood of infected animals during veterinary procedures or slaughter. Human to human transmission occurs if there is close contact with blood, secretions or other bodily fluids of the infected person. In humans the CCHF virus causes very severe viral haemorrhagic fever with a fatality rate of 30 to 40%.  There is no vaccine available for people or animals. april-veearts-1

Signs and symptoms in humans

Incubation following a tick bite is one to three days, with a maximum of nine days. After contact with infected blood or tissues, the incubation is five to six days with a maximum of thirteen days.
Symptoms start suddenly with a high fever, muscle aches, dizziness, pain and stiffness of the neck, headache, backache, sore eyes and light sensitivity. Early signs may include nausea, vomiting, diarrhoea, abdominal pain and sore throat. Sharp mood swings and confusion may occur. After two to four days the agitation gives way to sleepiness, depression and listlessness. The abdominal pain may be loca-lized to the upper right part of the abdomen and the liver will be enlarged. The heart rate will be fast, lymph nodes are enlarged and a pinpoint rash caused by bleeding into the skin is visible on mucous membranes of the mouth and throat and skin. The pinpoint bleedings may enlarge to form larger rashes and other haemorrhages.
Hepatitis may be present and by the fifth day severely ill patients may suffer from liver failure, rapid kidney damage or pulmonary failure. Death usually occurs in the second week of illness. In patients who recover, im-provement begins on the ninth or tenth day after onset of illness.

Diagnosis

Several laboratory tests are available to confirm the diagnosis. Collecting and handling samples is an extreme biohazard risk and maximum biological containment is necessary.

Treatment

Treatment is supportive and symptomatic. Patients must be hospitalized in an isolation ward. The antiviral drug ribavirin has been used with apparent benefit. When available, antibody-containing serum from recovered patients have been used.

Prevention and control

Because the tick-animal-tick cycle usually goes unnoticed and animals do not become clinically ill, control is made difficult. The tick vectors are also numerous and widespread and occur on livestock and wildlife. Tick control with acaricides is only an option in well-managed livestock production facilities.
After an outbreak at an ostrich abattoir, measures were taken to ensure that ostriches were quarantined and kept tick free for 14 days before slaughter to decrease the risk of ostriches carrying the virus at the time of slaughter.
Reducing the risk of infection in people
Greater awareness of the risk factors and measures to risk exposure is needed.

The risk of infection can be reduced in the following ways:

  • Wear long sleeves and long trousers in light colours to allow easy detection of ticks before they reach the skin.
  • Use approved acaricides on clothes to kill ticks.
  • Use insect repellent on skin and clothing.
  • Regularly examine skin and clothing for ticks and remove them safely with tweezers.
  • Eliminate or control tick infestations on animals in barns and stables.
  • Avoid areas where ticks are present in large numbers and seasons when they are most active. In the Western Cape ticks are most active during late Winter and early Spring months.
  • Wear gloves and protective clothing during veterinary procedures with exposure to blood and body fluids, as well as during slaughter.
  • Routinely treat animals with pesticides two weeks before slaughter. Ensure an adequate withdrawal period for the product.

Controlling infection in health-care settings

Health-care workers caring for patients with suspected or confirmed CCHF, or hand-ling specimens from them, should implement standard infection control precautions. These include basic hand hygiene, use of personal protective equipment, safe injection practices and safe burial practices.
Recommendations for infection control while providing care to patients with suspected or confirmed Crimean-Congo haemorrhagic fever should follow those developed by the WHO for Ebola and Marburg haemorrhagic fever.


Take note!

CORRECTION: In last month’s column we published a vaccination table for pigs. Zoetis, manufacturer of these products, informed us that Improvac is a product that is only sold to veterinarians because there is a safety factor to consider. All the other products are available through Co-ops. Please also note that Farrowsure Plus B is no longer available. It has been replaced by Farrowsure Gold B which is superior.