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A recent case series showed concerning trends of neurological conditions from mosquito-borne diseases impacting patients living in Canada and the United States.
Vanessa Meier-Stephenson, MD, PhD, FRCPC
Credit: University of Lethbridge
This content originally appeared on our sister site, ContagionLive.
In a recent case series published in Emerging Infectious Diseases, findings showed trends regarding the impact of the Jamestown Canyon virus (JCV), a mosquitoborne orthobunyavirus belonging to the California serogroup (CSG) viruses. The virus is identified as a prevalent pathogen in Canada and the US, with most cases resulting in either asymptomatic infection or mild febrile illness; however, certain cases showed potential to cause severe neurological diseases, including meningitis and encephalitis.
“There are a range of clinical manifestations from mild febrile illness to neuroinvasive forms described. We provide details of the prodrome to help guide the retrospective assessments, but certain on their own would be incredibly non-specific. Of the initial neurologic symptoms reported, 3 of the 5 described frontal and/or retro-orbital headaches,” lead author Vanessa Meier-Stephenson, MD, PhD, FRCPC, assistant professor, Department of Medicine, Division of Infectious Diseases, University of Alberta, told NeurologyLive®. “When CSG virus testing resumed in Canada in 2005, most CSG virus infections were shown to be caused by JCV, indicating the emergence of JCV as the primary CSG virus causing infection in Canada.”
According to the Centers for Disease Control and Prevention (CDC), for patients with symptoms, the time from mosquito bite to feeling sick (incubation period) ranges from a few days to 2 weeks.2
In this study, 2 cases, originating from Quebec and Nova Scotia, raised the most concern. These patients may have contracted JCV during travel to the northeastern US.
"JCV and other California Serogroup viruses are all mosquito-borne viruses that warrant consideration as we move into mosquito season across North America. Unfortunately, given that we only have supportive treatment to offer, investigations into underlying causes will often (and understandably) stop at the treatable diagnoses," Meier-Stephenson said. "A previous cross-Canada review of encephalitis cases revealed unknown etiologies in 50% of cases.3 This raises the case for the underdiagnoses of these viruses as contributors to the viral encephalitis burden in our population. This is partly why I'm eager to partake in an 'increased awareness' plug. One has to explicitly request these serologies from our diagnostic labs, so it would be up to the treating and consulting clinicians to first consider it."
On August 20, 2011, a 53-year-old man from Montreal, Quebec, presented with fever, fatigue, left-sided neck swelling and pain, and a rash on his lower back, buttocks, and genitalia. He reported a recent camping trip in Maine and New Hampshire, US.
According to the CDC, “Within 24 hours of admission, he became confused, and worsening hypotension and dyspnea developed, requiring intubation and vasopressors.”2
Serum and cerebrospinal fluid samples tested positive for JCV antibodies. The patient experienced confusion and hypoactive delirium during hospitalization. Despite being discharged on September 21, he continued to suffer from short-term memory loss, expressive aphasia, and muscle pain. 6 months later, his expressive aphasia persisted, but other symptoms had improved.
In June 2016, a 70-year-old man with psoriasis visited an emergency department in Nova Scotia after a fall. He experienced a frontal headache, episodic dizziness, and nausea with vomiting for 3–4 days. About 2.5 weeks before his admission, he had traveled in the US for 10 days. Various tests for infectious agents were negative except for JCV, which was confirmed in serum and cerebrospinal fluid samples.
According to the CDC, “The patient defervesced by day 2 but reported diffuse myalgias, although his headache was improving. His hospitalization was further complicated by a pulmonary embolism from which he recovered. After 5 weeks of rehabilitation and resolution of his symptoms, the patient was discharged.”2
All told, a limitation of the study is not testing for La Crosse virus (LACV), a CSG virus with diagnostic similarities to other CSG members. LACV testing was not included initially because of previous negative serologic screening studies, despite the presence of its primary vector in southern Canada. Including LACV testing in diagnostic algorithms for suspected CSG virus exposures in Canada is warranted considering potential virus expansion and increased prevalence.
These findings highlight JCV as an emerging threat in North America because of its potential to cause neurological diseases. The results underscore the need for enhanced surveillance, including testing for related viruses like LACV, and collaborative efforts among healthcare professionals and public health authorities to mitigate the impact of JCV on human health. Public health interventions focusing on mosquito control and early detection are important to prevent severe outcomes and minimize the burden.
"Seroprevalence studies certainly show that this virus can be found coast-to-coast. The borders we draw on a map are not upheld by the small mammals or ruminants that can harbour and amplify the viral spanse. This, coupled with the expanding catchment area of mosquitoes, will also contribute to the potential for further cases. Thus, travel between our countries, while many wonderful benefits, can for a small few lead to exposures to these potentially neuroinvasive viruses," Meier-Stephenson added. "Of note, humans are a 'dead-end' host, meaning that even if we're bitten by a mosquito, our viremia and viral levels aren't sufficient to infect more mosquitoes. So while we may travel between countries and bring viral souvenirs or suffer the sequelae therein, at least we're not contributors to the problem - just the canaries!"
