Credit CDC
#14,184
Late last year the CDC reported a Record Number Of Tickborne Infections In 2017 - and while many cases go unreported, and the actual numbers are much higher - the trend over the past dozen years is quite apparent.
There is a growing realization that the public health burden of tick and other vector borne diseases is likely much greater than previously appreciated.
- In 2013, the CDC revised their Estimate Of Yearly Lyme Disease Diagnoses In The United States, indicating that the number of Lyme Disease diagnoses in the country is probably closer to 300,000 than the 30,000 that are officially reported each year to the CDC.
- Seven years ago (see New Phlebovirus Discovered In Missouri) we learned about the new `Heartland Virus’ which made headlines when it was detected in two Missouri farmers with no epidemiological links and living 60 miles apart. Since then the number of cases – while small – has continued to grow (see MMWR: Heartland Virus Disease — United States, 2012–2013).
- And in late 2014 we learned of yet another new tickborne virus, this time detected in Bourbon County, Kansas (see CDC & EID Journal On The Recently Discovered Bourbon Virus).
- Other blogs on newly discovered tickborne illnesses in the United States include 2016's CDC: New Lyme-Disease-Causing Bacteria Species Discovered and 2013's EID Journal: Novel Bunyavirus In Livestock – Minnesota.
Epidemiology
There have been a limited number of Bourbon virus disease cases identified in the United States. Most patients reported exposure to ticks before becoming ill.
Clinical Signs and Symptoms
Patients with Bourbon virus have reported fever, fatigue, anorexia, nausea, vomiting, and maculopapular rash. They were also found to have thrombocytopenia and leukopenia. Based on the patient’s clinical signs and symptoms, they were thought to have a tickborne disease. Some of the patients found to be infected with Bourbon virus have died during their acute illness.
Treatment and Outcome
Currently there are no specific medications or therapies for Bourbon virus disease. Supportive therapy is recommended for any patient suspected of having Bourbon virus disease.
DiagnosisAll of which serves as prelude to a new research letter published in the EID Journal, which seeks to identify the wildlife reservoir host(s) of the Bourbon virus. While dogs and horses have been infected, early testing suggests that raccoons and deer are the biggest carriers.
There is no routine testing available for Bourbon virus. However, protocols are in place to allow people to be tested for evidence of Bourbon virus infections. Please contact your state health department if you have a patient with an acute illness that might be compatible with Bourbon virus infection.
Volume 25, Number 9—September 2019
Research Letter
Bourbon Virus in Wild and Domestic Animals, Missouri, USA, 2012–2013
Table
Appendix RIS [TXT - 2 KB]
Katelin C. Jackson1, Thomas Gidlewski, J. Jeffrey Root, Angela M. Bosco-Lauth, R. Ryan Lash, Jessica R. Harmon, Aaron C. Brault, Nicholas A. Panella, William L. Nicholson, and Nicholas Komar
Abstract
Since its recent discovery, Bourbon virus has been isolated from a human and ticks. To assess exposure of potential vertebrate reservoirs, we assayed banked serum and plasma samples from wildlife and domestic animals in Missouri, USA, for Bourbon virus–neutralizing antibodies. We detected high seroprevalence in raccoons (50%) and white-tailed deer (86%).
Bourbon virus (BRBV) was first isolated from a febrile patient with a history of tick bites in Bourbon County, Kansas, USA; the patient later died from severe illness in 2014 (1). Several additional human BRBV infections were reported subsequently from the midwestern and southern United States (2).
BRBV belongs to the family Orthomyxoviridae, genus Thogotovirus, which is distributed worldwide and includes Araguari, Aransas Bay, Dhori, Jos, Thogoto, and Upolu viruses (1,3). Thogoto and Dhori viruses have been associated with human disease (4–6). Viruses within the genus Thogotovirus have been associated with hard or soft ticks (7). Recent studies suggest that the lone star tick (Amblyomma americanum) is involved with BRBV transmission (2,3,8). These ticks feed primarily on mammals, which might play a role in BRBV ecology.
We evaluated banked animal serum and plasma for evidence of BRBV infection by using the plaque-reduction neutralization test to detect BRBV-reactive antibodies. We tested specimens of white-tailed deer (Odocoileus virginianus), raccoon (Procyon lotor), Virginia opossum (Didelphis virginiana), and various other mammals and birds from northwest Missouri, USA, for neutralizing antibodies against BRBV to identify naturally exposed host species and to implicate potential zoonotic amplifiers.
We collected specimens from wild and domestic vertebrates as described (9). We performed plaque-reduction neutralization tests (PRNTs) on serum and plasma samples by using Vero cell culture as described (9). In brief, we initially screened samples by diluting them 1:5 and mixing them with an equal amount of BRBV suspension containing ≈100 PFUs/0.1 mL. Samples that showed >70% reduction of plaques were confirmed by serial 2-fold titration in duplicate from serum dilutions of 1:10–1:320. We considered 70% PRNT titers >10 as positive.
We screened serum and plasma samples from 301 birds and mammals for BRBV-neutralizing antibodies. A total of 48 (30.8%) of 156 mammalian serum samples were positive at the 70% neutralization level (Table). Mammals with evidence of past infection included domestic dogs, eastern cottontail, horse, raccoon, and white-tailed deer. None of 26 avian species were seropositive (Appendix Table).
BRBV is probably transmitted to humans and other vertebrates by the lone star tick, an abundant arthropod in the southcentral United States (8). This virus was cultured from these ticks in northwestern Missouri in 2013 and eastern Kansas in 2015 (2,8). Our results indicated that mammals are frequently exposed to BRBV. This finding was expected because lone star ticks feed primarily on mammals, and rarely on birds.Our study corroborates that birds are not involved in BRBV transmission, and our data establish that the vertebrate host range for infection now includes >5 mammalian species, 2 of which are domestic animals (dogs and horses). Of the wildlife species, the seropositivity rate for white-tailed deer was high (86%), whereas Virginia opossums, despite a moderate sample size (n = 28), showed no evidence of virus exposure.(SNIP)
In conclusion, we have demonstrated that nonhuman vertebrates are exposed to BRBV. These findings are useful for future public health efforts and to better understand the ecology of BRBV. Specifically, we identified 2 candidate wildlife sentinels and potential domestic sentinels for tracking and possible early warning of BRBV transmission risk. However, whether any of these mammalian species are competent amplifier hosts for BRBV remains to be determined.
During this study, Ms. Jackson was an intern at the Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins CO. She is currently a doctoral candidate at Washington State University, Pullman, WA. Her research interests include a One Health approach to zoonotic infectious diseases.
The CDC offers the following advice on avoiding tick bites and tickborne illnesses.
Prevention
Protect yourself and your family by preventing tick bites. It only takes one bite from an infected tick to make you sick. There is no vaccine to prevent or medicine to treat infection with Heartland virus. Reduce your risk of getting sick by:
Preventing tick bitesPreventing ticks on your petsPreventing ticks in your yard
