Bioguard Corporation
Severe Fever with Thrombocytopenia Syndrome (SFTS) is an emerging infectious disease that was first reported in China in 2011. It is caused by the Severe Fever with Thrombocytopenia Syndrome virus (SFTSV) and is transmitted to humans and animals through the bite of an infected tick. The main clinical symptoms of SFTS include fever, vomiting, diarrhea, multiple organ failure, thrombocytopenia, leucopenia, and elevated liver enzyme levels. SFTSV has been detected in both domestic and wild animals, although most vertebrate animals were found to be sub-clinically infected with SFTSV.
Pathogen
SFTSV is a tick-borne virus belonging to the Genus Bandavirus (former Huaiyangshan Banyangvirus), Family Phenuiviridae.
Vector and Disease Transmission
The exact lifecycle and transmission mechanisms of SFTSV are not fully understood. However, ticks, particularly the Asian longhorned tick (Haemaphysalis longicornis), are believed to be the primary route of transmission. Other ticks, including Rhipicephalus sanguineus and Haemaphysalis concinna, have also been found to carry SFTSV. This suggests that ticks play a significant role in the transmission of SFTSV, similar to other members of the Phenuiviridae family, which are also known to be vector-borne.
SFTSV Transmission
Ticks are believed to be the primary vectors for SFTSV transmission, mainly through their bites. However, the virus can also be transmitted by infected animals or humans. Transmission of SFTSV from infected companion animals, such as cats and dogs, to humans has been reported through various routes.
Pathogenesis
Cytokine storm is thought to play a crucial role in the pathophysiology of SFTS. During the acute phase of the disease, the release of cytokines triggers a systemic inflammatory response. Histopathological examination of lymph nodes reveals necrosis and hemophagocytosis. The virus can be detected in the liver, spleen, adrenal glands, bone marrow, and lymph nodes. Thrombocytopenia may occur due to viral attachment to platelets, which are subsequently cleared by the spleen.
SFTSV and Animal
SFTSV has been detected in both domestic and wild animals; however, most vertebrate animals appear to be sub-clinically infected. Previous research indicates that antibodies (IgG/IgM) against SFTSV were found in goats and sheep (45.70%), cattle (36.70%), dogs (27.00%), chickens (9.60%), pigs (3.20%), and rodents (3.20%). A survey conducted in Taiwan identified SFTSV in Rhipicephalus microplus ticks collected from cows and goats, and antibodies against SFTSV were also detected in goats.
In experimental studies, four out of six cats infected with SFTSV died, displaying symptoms as severe or more severe than those observed in human patients (Scientific Reports, 2019). Additionally, two captive cheetahs in a Japanese zoo died of SFTS in 2017, and there have been reports of fatal SFTSV cases in cats in Japan.
References
- Casel MA, Park SJ, Choi YK. Severe fever with thrombocytopenia syndrome virus: emerging novel phlebovirus and their control strategy. Exp Mol Med. 2021 May;53(5):713-722.
- Seo JW, Kim D, Yun N, et al. Clinical Update of Severe Fever with Thrombocytopenia Syndrome. Viruses. 2021 Jun 23;13(7):1213.
- Sharma D, Kamthania M. A new emerging pandemic of severe fever with thrombocytopenia syndrome (SFTS). Virusdisease. 2021 Jun;32(2):220-227.
