JOURNAL OF THE LOUISIANA STATE MEDICAL SOCIETY
mask ventilation and bronchoscopy. 9,10 A mouse brain–derived CCHF vaccine has been developed in Bulgaria, but is not available elsewhere. In the absence of a universal vaccine, the best preventive measures for the TBHFs are tick avoidance and control, rapid burial of dead animals, and personal protective equipment for abattoir workers and medical personnel.
dead-end hosts during spring-summer blood-feeding. CTFV has also been transmitted by blood transfusion and congenitally.
Both CTFV and SRV can cause biphasic to triphasic febrile illnesses that mimic mild cases of Rocky Mountain spotted fever (RMSF) without rash. Leukopenia and thrombocytopenia are common laboratory manifestations of coltivirus infections. Complications are rare but may include meningoencephalitis, orchitis, hemorrhagic fever, pericarditis, and myocarditis. EYAV infections are more often complicated by CNS manifestations than American strain coltivirus infections. The most common differential diagnoses for the tickborne coltiviruses are other tickborne febrile diseases, most commonly RMSF in North America, which may be distinguished from CTFV and SRV infections by its characteristic rash and leukocytosis in most cases. Serologic diagnostic methods to detect anti-coltivirus antibodies include complement fixation, seroneutralization assay, immunofluorescence assay test (IFAT), ELISA, and Western immunoblot assay. The most specific and confirmatory laboratory diagnostic methods include rRT-PCR assays to identify CTFV-RNA (or the RNA of its cross-reacting serotypes, CTFV-Ca and SRV) or the isolation of coltiviruses after intracerebral inoculation of infected human blood into suckling mice. Treatment of all tickborne coltivirus infections is entirely supportive, and long-term complications are rare in tickborne coltiviral infections. Recovery is typically uncomplicated.
Tickborne Coltiviruses
The tickborne coltiviruses of the family Reoviridae are all double- stranded RNA viruses of the genus Coltivirus and include: (1) Colorado tick fever virus (CTFV), which is endemic in the United States and Canadian Rocky Mountain regions; (2) the California tick fever virus (TFV) of rabbits (CTFV-Ca); (3) the Salmon River virus (SRV) of Idaho, a serotype of CTFV; and (4) the European Eyach virus (EYAV) (Table 3). 10 The ixodid or hard ticks are the only vectors of the coltiviruses, with Dermacentor ticks (mainly D. andersoni ) being the principal vectors of CTFV and SRV in the Rocky Mountains of the U.S. and Canada and Ixodes ticks ( I. ricinus, I. ventalloi ) being the only vectors of EYAV throughout Europe. 10 Among the coltiviruses, CTFV has the widest host range, which includes squirrels, other rodents, rabbits, porcupines, marmots, deer, elk, sheep, and coyotes. The remaining coltiviruses have fewer, more specific wild animal hosts, including the black- tailed jackrabbit ( Lepus californicus ) for CTFV-Ca and primarily the European rabbit ( Oryctolagus cunniculus ) but also rodents, deer, domestic goats, and sheep for EYAV. The coltiviruses are maintained in nature by ixodid ticks that blood-feed on wild animal hosts with prolonged viremias and then transmit coltiviruses transstadially, but not transovarially. Infected nymphs hibernate over winter, and previously infected nymphs and newly infected adults then transmit coltiviruses to human
Prevention and Control of Tickborne Viral Infectious Diseases
There are a number of strategies that can be used in the prevention and control of tickborne viral infectious diseases, including immunization, personal protective measures, landscape management, and wildlife management. In the 1990s, a Lyme disease vaccine was developed for the United
TABLE 3
VIRUS NAME
GEOGRAPHIC DISTRIBUTION
TICK VECTORS
ZOONOTIC RESERVOIRS
Colorado tick fever virus (CTFV)
Rocky Mountain Regions of the U.S. and Canada, Northwest U.S.
Ground squirrels, chipmunks, wild mice, wood rats, wild rabbits, hares, porcupines, marmots, deer, elk, sheep, coyotes
Dermacentor andersoni
California hare coltivirus (CTFV-Ca)
Northern California
Black-tailed jackrabbit-hare ( Lepus californicus )
Dermacentor reticulatus, Ixodes apronophorus
Eyach virus (EYAV)
Western Europe: France and Germany
European rabbit ( Oryctolagus cunniculus ), wild rabbits, mice, mountain goats, domestic goats, sheep, deer.
Ixodes ricinus Ixodes ventalloi
Salmon River virus (SRV)
Idaho
Mammals - large reservoir probably similar to CTFV?
Dermacentor andersoni?
Table 3: The Tickborne Coltiviruses (Family Reoviridae, Genus Coltivirus )
J La State Med Soc VOL 170 MARCH/APRIL 2018 51
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