Baja California recorded more rickettsia infections in the first six months of 2026 than in all of 2025, and the tick-borne disease is now concentrated in two areas where many English-speaking residents live: Tijuana’s Zona Este and Ensenada. Dr. Adrián Medina Amarillas, the state’s epidemiological surveillance chief, confirmed the surge and said Mexicali and San Quintín are currently seeing the fewest cases. No formal health alert or fumigation campaign has been announced, so residents need to protect themselves.
Rickettsia in Baja California Has Killed Hundreds Since 2009
Rickettsia is a bacterial infection spread by the brown dog tick (Rhipicephalus sanguineus). It is not transmitted person to person or dog to person directly. The tick feeds on an infected dog, picks up the bacteria, then bites a human. Symptoms include high fever, severe headache, muscle pain, and sometimes a spotted rash on the wrists and ankles. Left untreated, the disease can cause organ failure and death. Early treatment with the antibiotic doxycycline is highly effective.
Baja California has been Mexico’s rickettsia hotspot for more than a decade. Between 2009 and 2019, the state reported over 4,000 confirmed cases and more than 300 deaths, according to federal epidemiological data. Mexicali’s poorer eastern colonias bore the brunt during that period, with stray dog populations and unpaved streets creating ideal tick habitat. A 2015 outbreak in Mexicali killed dozens and prompted emergency fumigation campaigns that sprayed thousands of homes.
The 2026 pattern is different. Cases have shifted west toward the coast. Dr. Medina Amarillas told El Sol de Tijuana that Tijuana’s Zona Este and Ensenada now account for the highest concentration of infections. Health officials have not fully explained the geographic shift, but several factors likely contribute: warmer coastal winters that extend tick breeding seasons, rapid residential construction near canyon edges and undeveloped land, and large populations of free-roaming dogs in both cities.
Zona Este and Ensenada Canyon Neighborhoods Face Highest Risk
Tijuana’s Zona Este is a broad area east of the city center that includes colonias like Mariano Matamoros, Sánchez Taboada, and Valle de las Palmas. Many of these neighborhoods sit against hillsides and open terrain where brown dog ticks thrive in brush and dry grass. Some colonias lack paved roads and consistent trash collection, conditions that support stray dog populations and tick reproduction.
Ensenada’s risk zones include canyon neighborhoods and semi-rural areas along the city’s eastern and southern edges. Colonias near Arroyo El Gallo and the hills above the Chapultepec corridor border undeveloped land where ticks are common. Parts of El Sauzal, north of Ensenada’s center, also feature brushy terrain adjacent to residential lots.
If you live near a canyon, vacant lot, or unpaved road in either city, your risk is elevated. Dogs that roam outdoors or walk through brush can carry dozens of ticks home. A single brown dog tick can lay up to 5,000 eggs, so one untreated dog can seed an entire yard or house with ticks within weeks.
Tick Prevention Products and What to Tell Your Doctor
Veterinary clinics across Baja California carry tick prevention products, though brand availability differs from the United States. NexGard (afoxolaner) and Bravecto (fluralaner) are both sold in Mexican veterinary pharmacies, often under the same brand names. Prices typically run between 400 and 900 pesos ($22 to $50 USD) per dose depending on dog weight. Seresto collars are also available at some pet supply stores and veterinary offices in Tijuana and Ensenada. Ask your vet for a prescription-grade oral or topical product rather than relying on over-the-counter sprays, which are less effective against brown dog ticks.
For humans, daily tick checks after outdoor activity are essential. Check behind ears, along the hairline, under arms, and around the waistband. Use fine-tipped tweezers to remove any attached tick by pulling straight up with steady pressure. Do not twist or crush the tick. Clean the bite area with rubbing alcohol.
If you develop a fever, headache, or muscle pain within two weeks of a tick bite (or even suspected tick exposure), go to an emergency room. Tell the doctor: “Sospecho rickettsiosis por garrapata” (I suspect tick-borne rickettsia). Ask specifically for doxycycline. Treatment is most effective within the first five days of symptom onset. After that window, the fatality rate climbs sharply. IMSS (Mexico’s social security health system) hospitals and private clinics in Tijuana and Ensenada are both familiar with the disease, but stating your suspicion clearly can speed diagnosis.
At home, keep yards clear of tall grass and brush. Seal gaps under doors and around foundations where ticks enter. Wash pet bedding weekly in hot water. If you find ticks in your home, a licensed pest control company can treat interior and exterior areas with acaricides. In Tijuana, municipal pest control services can sometimes be requested through the local delegación office, though response times vary.
State health officials have not announced any expanded fumigation or public awareness campaign for 2026. The state’s recently approved risk atlas, its first update in 14 years, may eventually map tick habitat against residential zones, but that tool is not yet operational. Until then, prevention falls on individual households. The next seasonal peak for brown dog tick activity runs through September, when temperatures remain warm and humidity rises along the coast. This story was first reported by El Sol de Tijuana.