Jul 25, 2014
Crimean-Congo Hemorrhagic Fever (CCHF)- An Emerging Zoonotic Problem in Pakistan
Crimean-Congo haemorrhagic fever (CCHF) is a widespread disease caused by a tick-borne virus (Nairovirus) of the Bunyaviridae family. The CCHF virus causes severe viral haemorrhagic fever outbreaks, with a case fatality rate of 10–40%.
The disease was first characterized in the Crimea in 1944 and given the name Crimean hemorrhagic fever. It was then later recognized in 1969 as the cause of illness in the Congo, thus resulting in the current name of the disease.
Crimean-Congo hemorrhagic fever is found in Eastern Europe, particularly in the former Soviet Union, throughout the Mediterranean, in northwestern China, central Asia, southern Europe, Africa, the Middle East, and the Indian subcontinent. Now a days outbreak have been reported in Pakistan in KPK province resulting in several casualities in KPK.
In Pakistan he virus was initially found in Loralai in 2006 where some butchers and livestock buyers died because of the disease. Domestic animals brought from Afghanistan to Pakistan through the border at Chaman carry the infectious ticks.
Ixodid (hard) ticks, especially those of the genus, Hyalomma, are both a reservoir and a vector for the CCHF virus. Numerous wild and domestic animals, such as cattle, goats, sheep and hares, serve as amplifying hosts for the virus. Transmission to humans occurs through contact with infected ticks or animal blood. CCHF can be transmitted from one infected human to another by contact with infectious blood or body fluids. Documented spread of CCHF has also occurred in hospitals due to improper sterilization of medical equipment, reuse of injection needles, and contamination of medical supplies.
A person cannot be infected by eating well-cooked infected meat since the virus does not survive cooking.
A study published in the journal Frontiers in Physiology in July 2012 states, “Vector-borne diseases (such as Congo or dengue fever) in people, as well as livestock, are common in KPK and Fata due to the limited use of vector control measures and access to livestock vaccines.”
“CCHF outbreaks typically occur following the migrations of nomadic people and livestock to district centres where they bring animals to sell and slaughter,” the study adds.
The virus replicates in the host tick as it passes from larval through adult stages (transstadial transmission), and it can also be transmitted from one generation to the next (transovarial transmission).
The length of the incubation period depends on the mode of acquisition of the virus. Following infection by a tick bite, the incubation period is usually one to three days, with a maximum of nine days. The incubation period following contact with infected blood or tissues is usually five to six days, with a documented maximum of 13 days.
The onset of CCHF is sudden, with initial signs and symptoms including headache, high fever, back pain, joint pain, stomach pain, and vomiting. Red eyes, a flushed face, a red throat, and petechiae (red spots) on the palate are common. Symptoms may also include jaundice, and in severe cases, changes in mood and sensory perception.
As the illness progresses, large areas of severe bruising, severe nosebleeds, and uncontrolled bleeding at injection sites can be seen, beginning on about the fourth day of illness and lasting for about two weeks. In documented outbreaks of CCHF, fatality rates in hospitalized patients have ranged from 9% to as high as 50%.
The long-term effects of CCHF infection have not been studied well enough in survivors to determine whether or not specific complications exist. However, recovery is slow.
CCHF virus infection can be diagnosed by several different laboratory tests i.e enzyme-linked immunosorbent assay (ELISA) ; antigen detection; serum neutralization; reverse transcriptase polymerase chain reaction (RT-PCR) assay; and virus isolation by cell culture.
Patients with fatal disease, as well as in patients in the first few days of illness, do not usually develop a measurable antibody response and so diagnosis in these individuals is achieved by virus or RNA detection in blood or tissue samples.
Tests on patient samples present an extreme biohazard risk and should only be conducted under maximum biological containment conditions. However, if samples have been inactivated (e.g. with virucides, gamma rays, formaldehyde, heat, etc.), they can be manipulated in a basic biosafety environment.
Treatment for CCHF is primarily supportive. Care should include careful attention to fluid balance and correction of electrolyte abnormalities, oxygenation and hemodynamic support, and appropriate treatment of secondary infections. The virus is sensitive in vitro to the antiviral drug ribavirin. It has been used in the treatment of CCHF patients reportedly with some benefit.
The antiviral drug ribavirin has been used in treatment of human disease in South Africa with apparent benefit. Both oral and intravenous formulations seem to be effective. Lack of significant clinical disease in livestock warrants no treatment considerations.
It is difficult to prevent or control CCHF infection in animals and ticks as the tick-animal-tick cycle usually goes unnoticed and the infection in domestic animals is usually not apparent. Furthermore, the tick vectors are numerous and widespread, so tick control with acaricides (chemicals intended to kill ticks) is only a realistic option for well-managed livestock production facilities.
Although an inactivated, mouse brain-derived vaccine against CCHF has been developed and used on a small scale in eastern Europe, there is currently no safe and effective vaccine widely available for human use.
Control strategies for human infection include the avoidance of tick bites through the use of repellents and appropriate protection when slaughtering or grooming animals. Movement of naive animals into endemic areas provides opportunity for vertebrate amplification of the virus and increasing occupational risk to butchers and hide preparers; tick control when naive animals and endemic stock are mixed is paramount. Medical personnel should use appropriate barrier nursing techniques and universal (standard) precautions when handling suspect patients.
Congo fever is a deadly disease with high case fatality rate and outbreaks have been reported in Pakistan during the several last years. The health ministry of Pakistan should take steps to control the outbreak of this deadly disease causing the death of many people every year. Proper tick control programmes should be implemented during the tick season to prevent the vector borne transmission of virus. Proper quarantine measures should be followed while importing the livestock. After 1st outbreak of virus and death of butchers in 2006 in Loralai authorities took immediate precautionary measures then and it was made mandatory for Afghan sheep to cross a pond filled with virus-killing medicine. This precautionary practice continued for some time that helped in the Congo virus prevention. However, the practice has not continued for a few years due to negligence. As the disease is also transmitted form infected humans to the healthy so illegal migration of people from Afghanistan to Pakistan should also be stopped as they may also be the source of infection. Government hospitals should be equipped with modern diagnostic tools for the early detection and control of virus.
Immediate steps should be taken by the government of Pakistan to control the outbreak of congo fever otherwise the disease may lead to increase in number of causalities day by day becoming a major health problem causing loss of precious human lives and effecting the economy of country.
• Dr. Samra Noreen, DVM, University College of Veterinary & Animal Sciences,The Islamia University of Bahawalpur;
• Dr. M. Tasawur Latif, MD, Uruguay;
• Usama Bashir, DVM (4th semester) Riphah College of Veterianry Sciences, Lahore