Introduction

The significant rise of the mosquito-borne disease La Crosse virus (LACV) encephalitis it is a common mosquito-borne disease in North America as it is the second reported disease after West Nile virus (WNV) encephalitis which is the most prevalent mosquito-borne disease.¹ 

Historically, the native North American tree hole mosquito, Aedes triseriatus, has been the vector of LACV transmission. In the past 20 years, there has been a significant geographic shift in LACV encephalitis cases. It had only been seen in small, poorly populated parts of the upper Midwest, with very few occurrences in the Appalachian region.¹

The name La Crosse was given to a disease from the county of Wisconsin as the disease started there and was noticed by adoctor in the 1960s. At that time, doctors reported that the disease impacts kids during summer, while nowadays, it is reported as pediatric arboviral encephalitis.²

What is La Crosse Virus?

The Bunyaviridae family of the California serogroup 18,19,20,45 is responsible for the disease La Crosse virus being transmitted from the eastern treehole mosquito (Aedes triseriatus). It is the primary host and vector for the La Crosse virus. Furthermore, there are also two species of mosquitoes known as Aedes albopictus and Aedes japonicius, which are reported to be vectors in the transmission of the La Crosse virus and play vital roles in maintaining the virus in endemic areas.²

What causes La Crosse Virus?

The Aedes triseriatus mosquito (treehole mosquito) is the one that transmits the La Crosse virus, which causes a disease known as La Crosse encephalitis. Vertical and horizontal transmission is the transmission cycle that viruses undergo. Vertical transmission happens when a female mosquito directly passes the virus to its offspring mosquitoes, which will rapidly spread the virus to humans or other mammals. However, horizontal transmission happens with small mammals (chipmunks, red fox, eastern cottontail and grey squirrels) through venereal transmission and mosquitoes, and the small mammals act as reservoir hosts. If humans are infected, they serve as dead-end hosts as they can't grow enough to feed infected mosquitoes.²

Epidemiology

High-risk areas and populations (geographical distribution, vulnerable groups)

La Crosse encephalitis is a rare disease that affects children during summer, as nearly 75% of cases reported are by paediatricians. Furthermore, many cases are reported during July and September in endemic areas such as rural areas of the central and midwestern states. There have been reports of cases of La Crosse virus in the United States, about 60 to 80 yearly, over the last decade.²

Research conducted discovered a total of 665 La Crosse encephalitis cases between 2003 and 2012. Also, another study reported cases of La Crosse encephalitis in North Carolina, Ohio, Tennessee, and Virginia, with 81% being pediatric between 2003 and 2012. The Center for Disease Control and Prevention (CDC) has reported that in 2009 and 2018, there were 68 reported cases of La Crosse encephalitis neuroinvasive disease though there is still underreporting of less severe cases.²

Symptoms of La Crosse Virus

La Crosse virus symptoms don't appear in most individuals affected by it, but for individuals, it takes 5 to 15 days to notice it.³

The symptoms of La Crosse virus are:

• Fever
• Headache
• Vomiting 
• Fatigue
• Nausea
• Lethargy

Inflammation of the brain is known as encephalitis a severe disease that is caused by the virus, and it most frequently in individuals who are less than 16 years old. Also, the symptoms are:³

• Coma
• Vision loss
• Seizures
• Muscle weakness
• Numbness
• Paralysis
• High fever
• Neck stiffness
• Stupor disorientation

The duration of encephalitis healing depends on the impact of the symptoms and can persist over time. This could be from behavioural issues or recurrent seizures. Furthermore, the majority of patients recover from it but there is a chance of less than 1% to die.³

Treatment for La Crosse Virus

Currently, no treatment is available for LACV. Furthermore, there is no antiviral medicine found and antibiotics are effective in dealing with viruses.⁴

Individuals having severe illnesses can go to the hospital to seek help by getting following these supportive therapy:⁴

• Respiratory support
• Intravenous (IV) fluids
• Prevention from other infections

Preventive measures against Lacrosse Virus

To prevent LACV you should avoid mosquito bites by following these strategies.⁴

• Apply oil from lemon eucalyptus on your clothes or bare skin
• Apply insect repellent consisting of IR3535, picaridin or DEET
• Wear long pants and sleeves inside or outside the house
• Use mosquito nets in your windows and doors to keep them out
• Remove flower pots, buckets, barrels and other containers to eliminate mosquito breeding
• Drain out the water from tyre swings by drilling hole and kiddie pool and dry it before storing it in your house
• Make sure you clean potential breeding areas to reduce the number of infected eggs developing into infected mosquitoes as LACV can survive winter and in the spring the egg will hatch 
• Apply sand to fill the tree holes in the yard to prevent Aedes mosquito species from laying their eggs

Healthcare team outcomes

LACV is difficult to diagnose due to its low index of suspicion and non-specific symptoms. Hence, to manage the LACV, many interprofessional healthcare professionals will need to work together to manage the LACV encephalitis. In addition to doctors and nurses, a dedicated team, including respiratory therapists, dietitians, and physical and occupational therapists plays a vital role in caring for patients who need critical care. Social workers, along with mental health and developmental specialists, provide essential support, especially since patients may face long-term challenges like behavioural issues, personality changes, and cognitive delays.²

Public education and awareness campaigns

Epidemiologists and public health specialists are key players in educating communities and providing public health services to those affected by this disease. The total burden of La Crosse encephalitis, including healthcare costs and long-term medical expenses, ranges from $49,000 to $3 million. For individuals severely affected by La Crosse encephalitis, the impact on their productive life years is significant, estimated to affect 18% to 92%.²

Summary

La Crosse virus (LACV) encephalitis, spread mainly by the Aedes triseriatus mosquito, has been increasing in North America. This disease particularly affects children in rural areas during the summer months. Symptoms can vary from mild fever and fatigue to severe brain inflammation, which may lead to long-term cognitive and behavioural problems. Each year, around 60 to 80 cases are reported, mostly in kids. While there is no specific treatment for LACV, supportive care like respiratory assistance and IV fluids can help. To prevent LACV, it's important to avoid mosquito bites by using repellents, wearing protective clothing, and eliminating standing water where mosquitoes breed. Public health education and coordinated care from healthcare professionals are essential in managing and preventing this disease.