The Centers for Disease Control and Prevention (CDC) has singled out Lyme Disease (LD) as currently the most common and fastest growing vector-borne, infectious disease in America, but the Texas Lyme Disease Association (TXLDA) says many Texans and Texas medical professionals are unaware of the risks posed by Lyme and other tick-borne diseases in the state. Since 2002, the CDC has reported 783 confirmed cases of Lyme disease in Texas, but TXLDA contends that the number of those infected is likely to be dramatically higher because there is no reliable test to diagnose the disease. As a result, many sufferers are never aware they are infected.
According to Texas A&M University’s Lyme Lab, LD is a zoonotic, tick-borne illness caused by the spirochetal bacterium Borrelia burgdorferi, and it is the most prevalent arthropod-borne infection in the United States, with a total of 22,572 human cases of Lyme disease reported to the CDC in 2010. Dogs, cats, horses, and cattle can also suffer from LD. Infected tick vectors transmit the LD causative agent while biting humans and susceptible domestic animal species.
The Lab notes that a significant increase in the number of reported cases has been observed in the past few years, classifying Lyme disease as a re-emerging infection. Lyme borreliosis is, therefore, an important public health issue, particularly in endemic areas where it contributes to significant rates of morbidity. Lyme disease occurs as a multi-systemic disorder leading to carditis (10% of untreated adults), arthritis (60% of the cases) and other neurological symptoms. Moreover, there are few therapeutic solutions for Lyme disease patients and there are no effective vaccines available on the market.
A recent study conducted by an international research team from seven U.S. and Mexican universities and institutions has confirmed that risk for Lyme Disease is significant in the state of Texas and northern parts of Mexico, and determined that the tick-borne bacterial infectious agent that causes LD is now endemic to the Texas/Mexico border region and likely to remain so, with a higher probability of occurrence along the Gulf Coast.
The researchers, including representatives of the College of Veterinary Medicine & Biomedical Sciences at Texas A&M University, the University of Texas, and Texas State University have effectively refuted previous contention and speculation that Lyme disease is relatively non-existent in the southern United States.
The study, which was funded in part by a grant to improve the diagnosis of LD in veterinary medicine, is published online by the journal Parasites and Vectors, entitled “Implications of climate change on the distribution of the tick vector Ixodes scapularis and risk for Lyme disease in the Texas-Mexico transboundary region” (Parasites & Vectors 2014, 7:199 doi:10.1186/1756-3305-7-199), coauthored by equal contributors Teresa P. Feria-Arroyo and Ana L. Cavazos of the Department of Biology, The University of Texas-Pan American, Edinburg, Texas; Ivan Castro-Arellano of the Department of Biology, College of Science and Engineering, Texas State University, San Marcos; Guadalupe Gordillo-Perez and Javier Torres of Unidad de Investigacion en Enfermedades Infecciosas, Centro Medico Nacional SXXI, IMSS, Distrito Federal 06720, Mexico; Margarita Vargas-Sandoval of Facultad de Agrobiologa, Universidad Michoacana de San Nicols de Hidalgo, Uruapan, 60090 Michoacan, Mexico; Abha Grover and Maria D Esteve-Gassent of the Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station; Raul F Medina of the Department of Entomology, College of Agriculture and Life Sciences, Texas A&M University, College Station; and Adalberto A Prez de Len of USDA-ARS Knipling-Bushland U.S. Livestock Insects Research Laboratory, Kerrville, and Texas A&M Department of Veterinary Pathobiology Corresponding author is TAMU’s Maria D Esteve-Gassent. The electronic version of this Open Access paper is complete and can be found online at: http://www.parasitesandvectors.com/content/7/1/199
The coauthors observe that disease risk maps are important tools that help ascertain the likelihood of exposure to specific infectious agents, and that understanding how climate change may affect the suitability of habitats for ticks will improve the accuracy of risk maps of tick-borne pathogen transmission in humans and domestic animal populations. Lyme disease (LD) is the most prevalent arthropod borne disease in the US and Europe, and is caused by the bacterium Borrelia burgdorferi which it is transmitted to humans and other mammalian hosts through the bite of infected Ixodes ticks. THey note that LD risk maps in the transboundary region between the U.S. and Mexico are lacking, and moreover that none of the published studies evaluating the effect of climate change in the spatial and temporal distribution of I. scapularis have focused on this region.
The researchers report that the area covered by their study included Texas and a portion of northeast Mexico, subsequently referred to as the Texas-Mexico transboundary region. Tick samples were obtained from various vertebrate hosts in the region under study. Ticks identified as I. scapularis were processed to obtain DNA and to determine if they were infected with B. burgdorferi using PCR. A maximum entropy approach (MAXENT) was used to forecast the present and future (2050) distribution of B. burgdorferi-infected I. scapularis in the Texas-Mexico transboundary region by correlating geographic data with climatic variables.
Of the 1,235 tick samples collected, the scientists report that 109 were identified as I. scapularis, and B. burgdorferi infection was detected in 45% of the I. scapularis ticks collected. The model presented here indicates a wide distribution for I. scapularis, with higher probability of occurrence along the Gulf of Mexico coast. Results of the modeling approach applied predict that habitat suitable for the distribution of I. scapularis in the Texas-Mexico transboundary region will remain relatively stable until 2050.
The coauthors conclude that with the Texas-Mexico transboundary region, appearing to be part of a continuum in the pathogenic landscape of LD, and with Lyme presumably there to stay, forecasting based on climate trends provides a tool to adapt strategies in the near future to mitigate the impact of LD related to its distribution and risk for transmission to human populations in the region.
“Many Texans falsely believe they are not at risk of contracting Lyme or other tick-borne diseases in this state, but I know otherwise,” observes Debra McGregor, TXLDA Vice President for Education, whose fourteen-year-old son, Reed McGregor was bitten by multiple ticks on a Boy Scouting trip in June of 2009. Reed suffered with multiple systemic neurological issues and was unable to attend school, but his mother could not find a physician in Houston who could help her son. After second opinions in New York City and Louisiana, she was finally able to find a doctor out of state who specialized in Lyme and tick-borne diseases, and after three years of suffering, Reed is now symptom free.
“Once my son received a proper diagnosis, we were finally able to get him the treatment he needed to return to his old self,” says Ms. McGregor. “By building awareness of the risk, we hope to help all Texans understand the serious risk of contracting tick-borne diseases and encourage them to take steps to protect themselves from ticks whenever they spend time outdoors.”
Ms. McGregor who has a B.S. in Nursing from the University of Texas/Austin, and spent many years of her clinical career specializing in Surgery at St. Luke’s/THI in Houston and St. Joseph’s Hospital in Bryan, TX, subsequently, spending many years as a Nurse Legal Consultant for Andrews Kurth LLP in Houston, TX. is cited by The Rancher affirming that the findings of the U.S./Mexican study are crucial for the improvement of diagnosis and treatment of Lyme disease in Texas, noting “The information this study gives us is a game-changer; now that Lyme disease-causing pathogens have been proven to exist in Texas, physicians should be able to deliver earlier diagnosis and treatment.”
According to Ms. McGregor, TXLDA receives two to three requests per day from patients with either symptoms or confirmed cases of Lyme Disease, seeking medical help, with the number of requests tripling in the past year alone. She says early detection and treatment are key to providing patients with a cure, and that confusion and disagreement among physicians has left thousands of Texans out in the cold while trying to get well, irrespective of whether they were exposed out of state or in Texas.
Because diagnosis and treatment of Lyme disease is still evolving, TXLDA emphasizes that prevention is critical, and recommends when engaging in outdoor activities to wear light-colored clothing so that crawling ticks can be seen. The organization goes on to suggest the following: tuck pant legs into boots or socks so that ticks do not have access to skin and may more easily be seen; use insect repellents with DEET or Permethrin (cream 5%) in high-risk areas as well as tick and flea preventatives on pets; inspect yourself, your children, and your pets frequently for ticks, and remove any attached ticks promptly using proper removal procedures; avoid areas with high grass. When hiking, stay on the trails; don’t sit on stone walls; and wear shoes and socks, not sandals. According to the Lyme Disease Association “Ticks are most likely to be in woods, where woods meet lawn, where lawn meets fields, tall brush/grass, under leaves, under ground cover (low growing vegetation), near stone walls or wood piles, shady areas, around bird feeders, and in outside pet areas.”
The TAMU Lyme Lab’s research interest is mainly directed toward understanding the distribution of infected ticks in Texas as well as in the development of a pan-specific Lyme test for use in Veterinary medicine and surveillance programs. Pooling these two efforts, the goal is to map the state of Texas to determine where are the high-risk areas for Lyme disease transmission, and to identify new vaccine targets to prevent Lyme disease. As part of this effort the Lab’s scientists are trying to sequence the gene expression of this bacterium at different time points during the infection process by means of Next Generation Sequencing such as the Ilumina technology.
Distribution of Lyme Disease in Texas. Cumulative cases from 2000 to 2010 – Image Credit TAMU Lyme Lab
For more information on TAMU research on Lyme Disease, see:
Texas Lyme Disease Association
Texas A&M University Lyme Lab
Parasites & Vectors
Texas A&M University Lyme Lab