Abstract
Crimean-Congo hemorrhagic fever (CCHF) is a pathogenic tick-borne disease caused by a single-stranded negative-sense RNA virus classified within the Nairovirus genus of the family Bunyaviridae. Cases of CCHF have been registered in Tajikistan since the disease was first brought to medical attention in 1944. However, historical Tajik manuscripts describe the features of hemorrhagic fever associated with ticks, indicating that the disease might have been known in this region for many years before it was officially characterized. Here we review the historical context of CCHF in Tajikistan, much of which has been described over several decades in the Russian literature, and include reports of recent outbreaks in Tajikistan.
Introduction
Initial diagnosis of CHF disease was difficult, principally because the differential symptoms could be mistaken with those of other diseases such as sandfly fever, malaria, typhus, leptospirosis, Omsk hemorrhagic fever, Q fever, and yellow fever. In addition, another uncharacterized disease was reported in the southern regions of the former Soviet Union: Central Asian hemorrhagic fever (CAHF) (Casals et al. 1966). It was not until 1967 that the agent of CHF was characterized utilizing suckling mouse inoculation techniques for virus isolation (Chumakov 1968). This breakthrough formed the foundation on which research into CHF and similar diseases could be based, and provided a turning point for the understanding of this disease. Subsequent investigations into CHF, CAHF, and the novel Congo virus reported in Africa (Simpson et al. 1967, Woodall et al. 1967) showed that all three diseases were caused by the same etiological agent (Casals 1969) and therefore could be considered as a single disease. From 1979, CCHF was adopted as the generic name for the disease, and the etiological agent was termed CCHF virus (CCHFv) (Hoogstraal 1979).
CCHF Diagnosis in Tajikistan
CCHF is endemic in Tajikistan, and human cases have been ascribed to this disorder since medical recognition of the disease in 1944. Formal CCHF diagnosis in Tajikistan has been undertaken by The Science and Research Institute of Preventative Medicine in Dushanbe since 1961; however, it was not until 1968 that the first etiologically confirmed cases of CCHF were diagnosed using specialized techniques (Chernovsky et al. 1968, Chumakov 1968).
Immunological tools based on the complement fixation assay were the mainstay of laboratory diagnosis for over two decades. Originally, these were developed locally through the purification of virus antigen via passage in suckling mice and subsequent processing. However, since 1993, commercial CCHFv enzyme-linked immunosorbent assay (ELISA) kits have been available (Ivanovsky Virology Institute, Moscow, and Vektor-Best, Novosibirsk), and primary diagnosis of CCHF is now routinely based on these assays, allowing for rapid confirmation of CCHFv antigen or reactive antibodies to CCHFv. In recent years, PCR and real-time PCR techniques have been adopted to complement data from ELISA tests.
Clinical disease and epidemiology
The clinical symptoms of the disease in Tajikistan have been documented (Chernovsky et al. 1968, Blyakher et al. 1971, Pak et al. 1975), and there appears to be both moderate and severe clinical forms of disease. Both forms are characterized by malaise, tachycardia, and hemorrhage, although all of these symptoms are more pronounced in the severe form of the disease. Severe cases were characterized by abundant hemorrhages from several organs, as well as pronounced blood loss. Moderate cases of disease were typified by less serious hemorrhagic symptoms that remedied 2–3 days after onset. Analysis of contacts during recent outbreaks also indicates the presence of asymptomatic infections.
CCHF remains a rare disease even in endemic countries. In Tajikistan the average number of human cases reported each year typically ranges from 1 to 6, although epidemic years characterized by over 20 cases are sometimes reported (21 cases in 1967, 26 cases in 2001, 29 cases in 2007, 37 cases in 2008, and 29 cases in 2009). The majority of Tajik reports show that cases associated with tick bite have a lower case fatality rate (∼22%) than those associated with direct contact with infected blood (∼50%), which possibly reflects the viral load of the inoculum. The ratio of male to female cases is 2:1, correlating with occupational exposure to either tick vectors or infected blood. As in other countries the predominant risk groups include farmers, field workers, butchers, and hospital staff. Overall, the average case fatality rate in Tajikistan is 24%.
Ecology
In Tajikistan, the majority of human cases are a direct result of a bite from an infected tick. Hyalomma anatolicum is considered to be the principal vector accounting for over 82% of ticks collected in endemic areas (Kuima 1975). Other potential vector species have been recorded, including Hyalomma marginatum, Hyalomma scupense (formerly Hyalomma detritum), Hyalomma impeltatum, Hyalomma dromedarii, Hyalomma turanicum, and Dermacentor marginatus. Several studies have reported the isolation of CCHFv from Hy. anatolicum and Hy. scupense collected in Tajikistan (Tsilinsky et al. 1972, Pak 1973, Daniyarov 1975); additionally, these data indicated that human cases of CCHF coincided with the geographic range of the predominant tick vectors in the region. Unsurprisingly, the seasonality of human cases strongly corresponds with that of the tick season with the majority reported between March and October, peaking between June and August (Chernovsky et al. 1968, Pak 1973). To date, no cases have been reported during the winter months when daily average temperatures are below that required for tick activity. The larvae and nymphs of Hy. anatolicum typically parasitize only wild and domestic animals and birds, and are rarely associated with biting humans (Chernovsky et al. 1968).
CCHFv has been isolated from ticks from all regions of Tajikistan except the extreme altitudes in the Pamir Mountains. However, the vast majority of human cases occur in the southern region, where it is likely that the lower altitude and southerly latitude in comparison to the rest of the country allow for larger tick populations and therefore more chance of human exposure to the virus. Indeed, tick surveys in this region have noted large tick populations, some finding 25 times more ticks in comparison to similar areas in other parts of the country (Kuima 1971, Pak 1975). In the summer months it is not unusual to find >100 Hy. anatolicum ticks on a single cow. Risk for human exposure is greatest in cattle pastures and cattle housing, where cracks and crevices in the clay walls support all stages of Hy. anatolicum ticks. Unfed adult ticks can survive up to 4 years in such conditions and are of greatest risk to humans when cattle are not returned to the tick-infested pastures or housing, resulting in ticks aggressively seeking a host to feed on.
Treatment and prevention
Medical treatment typically involves palliative measures directed at water and electrolytic balance, managing hemorrhagic symptoms, and reducing associated pain. Although the level of benefit from the antiviral drug Ribavirin in treating CCHF is still under assessment (Soares-Weiser et al. 2010, Ascioglu et al. 2011), it is offered in the treatment regimen for suspected CCHF cases in Tajikistan. However, the extreme cost of the drug (∼100 USD per patient course), combined with lack of substantial clinical evidence, has led to low patient uptake.
Public health campaigns have placed the emphasis on prevention rather than treatment. These promote the use of personal protective measures such as insect repellents for farmers and forestry workers, and advice to reduce the incidence of tick bites. For healthcare workers, basic medical strategies such as patient isolation and correct use of personal protective equipment play a significant role in reducing the incidence of nosocomial transmission.
Results
Case reports
Over the last 20 years there have been four separate instances where numerous human cases of CCHF have resulted from a single exposure. The following reports will document the progression of these outbreaks and the clinical outcome of the patients involved. The information presented in these case reports (A–D) is also summarized in Table 1.
In total, 20 cases of clinical disease were recorded: 9 were described as the severe form of disease (all of which were fatal); 11 were described as the moderate form of the disease (all of which recovered). Serological testing of patient contacts identified 9 asymptomatic infections where reactive antibodies developed, but no major clinical indicators of CCHF disease presented.
CCHF, Crimean-Congo hemorrhagic fever.
Case report A: Shaartuz district, 1991 (9 cases, 3 deaths)
In June 1991, nine cases of CCHF, including three fatalities, were confirmed after an outbreak of hemorrhagic disease in the Shaartuz district. The initial exposure to CCHFv appears to have been direct blood exposure after the slaughter of an infected cow. Seven of the nine cases associated with this outbreak were present at the slaughter of the animal, and the remaining two cases had contact with fresh meat soon after slaughter. The owner of the slaughtered cow, the index case (patient A1), became feverish on June 23, 1991, and was hospitalized on June 28 with an initial diagnosis of exacerbated gastric and duodenal ulcers in combination with radiculitis. Admission symptoms included severe headache, epigastric pain, and vomiting. Hyperemia and hemorrhagic manifestations such as ecchymosis, petechial rash, and gingival bleeding developed rapidly after hospitalization. The increase in severity of hemorrhagic symptoms clearly matched the deterioration in the patient, who died during the night on the first day of hospitalization.
Two further cases (A2 and A3) died 2 days later, with similar symptoms to patient A1, leading to initial suspicion of CCHF. Samples were sent to The Science and Research Institute of Preventative Medicine in Dushanbe for analysis, and immediate contact tracing began. Six additional cases (patients A4–A9) were identified, all of who developed a less severe clinical disease typified by fever (∼39°C), headache, muscle and joint pain, petechial rash, and gingival bleeding. In these milder cases, hemorrhages disappeared within 8 days of onset of illness, and all these patients made a full recovery.
Laboratory diagnosis of CCHF was confirmed for seven of the nine cases using complement fixation and ELISA (IgG and IgM); samples were not available for two of the fatal cases (A1 and A3). Follow-up testing of the nonfatal cases showed a fourfold increase in reactive IgG antibodies. Contact tracing revealed a further 19 people with potential exposure to the virus, including 11 medical workers. However, no further clinical cases were observed and all contact samples tested negative for CCHFv using complement fixation and ELISA.
Case report B: Tursunzoda district, 1993 (5 cases, 1 death)
In 1995, a nosocomial outbreak of CCHF was recorded in Tursunzoda district. The index case (B1) was a 40-year-old man who lived and worked on a collective farm in the Chirtak district. The initial exposure to CCHFv was likely to be as a result of a bite from an infected tick. Onset of illness for patient B1 began on May 26, 1993, with low-grade fever and stomach pain. On May 28 the first hemorrhagic symptoms appeared with small skin hemorrhages on the feet and trunk. Nasal hemorrhages began on May 29, and increased in severity over a 24-h period to the extent that he sought medical assistance. Upon hospitalization on May 30 his condition was noted as being severe: a temperature of 40°C; punctuated hemorrhages on the shoulders, arms, trunk, and feet; impaired respiration; and a weak pulse. Analysis of blood samples showed marked leucopenia and thrombocytopenia.
Because of extensive epistaxis, nasal packing was performed on numerous occasions. Intestinal hemorrhaging began on June 1, and respiratory function rapidly deteriorated. On June 3, 1993, patient B1 went into respiratory arrest, and died shortly after, despite measures including artificial ventilation.
In total, 15 medical staff provided assistance to patient B1, of who 8 were deemed to have carried out activities that could have exposed them to the virus. All eight at-risk personnel were monitored for signs of CCHF symptoms, and blood samples were collected each day for testing. Four medical workers (B2, an otolaryngologist; B3, an infectious disease specialist; B4, a nurse; and B5, a nursing assistant) developed reactive IgM antibodies to CCHFv. Patients B2, B4, and B5 developed symptoms consistent with the moderate form of the disease, including minor hemorrhagic symptoms such as maculopapular rash, vomiting, and/or epistaxis, all of which resolved after 2–3 days. Patient B3 developed a subclinical infection. All four medical staff who appear to have contracted CCHFv from patient B1 made a full recovery.
Case report C: Dangara district, 2001 (6 cases, 2 deaths)
A nosocomial outbreak of CCHF occurred in the Dangara hospital in 2001. The index case (patient C1) was a 62-year-old man; his exposure to CCHFv is unknown. He was admitted to the hospital on the third day of illness (June 28, 2001) with headache, high temperature, epigastric pain, vomiting, and malaise. The initial diagnosis upon admission was exacerbation of gastric and duodenal ulcers. After an endoscopic assessment, immediate surgery was recommended on account of excessive gastric hemorrhaging thought to be caused by the ulcers. Surgical intervention failed to alleviate the condition, and the patient died hours after surgery. The cause of death was attributed to complications arising from gastric ulceration.
On July 1, 2001, a nurse (patient C2) who assisted in the emergency surgery performed on patient C1 was hospitalized with symptoms, including elevated temperature (39°C), headache, gastric pain, and painful hands and feet. The onset of epistaxis and a petechial rash on the hands and feet began ∼24 h after admission. During the following 2 days her condition deteriorated: intestinal and uterine hemorrhagic symptoms developed, with increased epistaxis and the development of large ecchymoses, which covered the majority of the body. Cardiac complication developed due to massive fluid loss as a result of the extreme hemorrhaging, and the patient died on July 4.
This second case of severe hemorrhagic illness in a short period in the same hospital, combined with an epidemiological link between the patients, led to a tentative diagnosis of CCHF. Samples were sent to The Science and Research Institute of Preventative Medicine in Dushanbe for analysis, and immediate contact tracing began. Five medical personnel responsible for treating patients C1 and C2, as well as a family member of C2, were identified as having a high risk of exposure to CCHFv. All six individuals were put under medical surveillance, and regular samples sent for testing. Four of the six contacts (C3–C6) tested positive for reactive IgM antibodies, and a minimum of a fourfold increase in the titer was demonstrated with subsequent samples. Patients C3 and C4 were medical workers associated with the care of patient C1, patient C5 was a medical worker associated with the care of patient C2, and patient C6 was a close family member of patient C2. Patients C3 and C6 developed symptoms associated with the moderate form of the disease: headache, malaise, and mild hemorrhagic rashes on the skin that disappeared after a few days. Both patients made a complete recovery. Patients C4 and C5 failed to develop any significant symptoms of disease despite the presence of reactive antibodies, suggesting a subclinical infection.
Case report D: Tursunzoda district, 2009 (9 cases, 3 deaths)
On July 26, 2009, a 50-year-old man (patient D1) was admitted to the contagious isolation ward of the central regional hospital with symptoms, including severe headache, elevated temperature, nasal hemorrhage, and vomiting. Hemorrhagic symptoms increased rapidly after admission with pronounced skin petechiae, ecchymosis, severe epistaxis, subconjunctival hemorrhage, and pronounced hyperemia. Patient D1 died during the night on the day of admission.
A tentative diagnosis of CCHF was made shortly after admission, and immediate identification of potentially exposed medical personnel was undertaken. Seven medical workers were determined to potentially have been exposed to CCHFv, and were placed under medical surveillance.
On August 2, a member of the medical staff (patient D2) developed headache and a low-grade fever. Mild hemorrhagic symptoms began the following day, and over the course of the next 24 h grew in severity. By August 4, patient D2 was suffering from severe nasal, skin, and intestinal hemorrhages. Patient D2 died on August 6 due to cardiac complications brought on by the hemorrhagic manifestations.
On August 3, the brother of the index case became the third person to be hospitalized with symptoms of CCHF (patient D3). Patient D3 had cared for patient D1 at home before he sought medical assistance. Symptoms upon admission included headache, high temperature (>39°C), nasal and gingival hemorrhaging, as well as pain in the hands, feet, and back. Full clinical examination revealed subconjunctival and skin hemorrhages, and blood analysis indicated leucopenia and thrombocytopenia. Patient D3's condition gradually deteriorated over the course of the next 48 h, and he died on August 5.
Two further cases were documented over the following days: a medical worker (patient D4) associated with the care of patient D1 developed a low-grade fever and general malaise, and a relative (patient D5), who had cared for both patients D1 and D3 before they sought medical assistance, complained of mild headache. Both patients D4 and D5 were monitored in hospital, but neither developed any significant symptoms of disease, although both patients showed a greater than fourfold increase in specific CCHFv antibodies via ELISA testing.
In addition to these five cases, diagnostic assessment was carried out on a further 46 close contacts and medical workers deemed to have had potential exposure to CCHFv. Four cases tested positive by ELISA testing of paired sera; none reported any clinical symptoms of disease. In total, the 2009 outbreak of CCHF resulted in three fatal cases (the index case, the brother of index case, and a medical worker), and six mild/asymptomatic cases that did not produce any hemorrhagic symptoms. Patients D2–D9 all had exposure to infected blood of patient D1 either in the home or in the hospital setting.
Discussion
Many Soviet manuscripts lay testimony to the importance of CCHF in Tajikistan. Since 1944, when clinical reporting began, over 400 cases of disease have been documented. It has been reported that sporadic cases of CCHF in Tajikistan have been misdiagnosed as Werlhof's disease, hemorrhagic diathesis, and capillary toxicosis, among other disorders (Pak 1972), and in two of the case reports documented in the Results section, the initial diagnosis of CCHF patients was exacerbation of ulcers.
Because of the high case fatality rate associated with tick-bite transmission of the diseases (∼22%), and the extremely high case fatality rate associated with nosocomial/direct blood contact transmission (∼50%), it is of great importance that this disease should be quickly and accurately detected to allow implementation of appropriate medical techniques to reduce further spread. The continual detection of CCHFv in tick populations, combined with regular human cases of disease, shows that CCHFv is endemic in Tajikistan, and is a healthcare issue that requires managing.
It is noticeable that of the 5 years that have resulted in >20 confirmed cases of CCHF in Tajikistan (1967, 2001, 2007, 2008, and 2009), 4 of them have occurred in the last 10 years, and the 3 years with the most recorded cases have been in the 3 most recent years for complete data. Although it is impossible to evaluate all contributing factors to this phenomenon, it is likely that the increase in funding for nationwide CCHF diagnosis, combined with the implementation of more sensitive molecular and serological assays, plays a significant role in the recent upward trend of positive cases.
Ongoing international collaboration provides the latest information, training, diagnostic assays, and equipment to be disseminated to appropriate laboratories, and the long-term aim is to establish a high containment laboratory in Dushanbe capable of carrying out all molecular and virological techniques associated with CCHF diagnosis and research.
Footnotes
Acknowledgments
The authors would like to acknowledge the financial support from the UK Global Partnership Biological Engagement Programme in forming this international collaboration.
Disclosure Statement
The authors declare no conflicting interests.