There are many known causes of dementia. One of these causes are bacteria. Bacteria are usually ignored despite its historical and current significance in dementia research. A hundred years ago it was well known that syphilis—a bacterium—was the only known cause of dementia. The bacteria eat away at the nerves until it reaches the brain where it destroys the brain from the inside. At the end, the expression of long-term syphilis is dementia—Neurosyphilis. Alois Alzheimer wrote the textbook on neurosyphilis before his supervisor Emil Kraepelin propelled him into the history books by define Alzheimer’s disease as a new disease in 1911. 
Neurosyphilis was very common in the 1900s. Between one in four to one in ten people in mental institutions were there because of neurosyphilis. Eventually syphilis kills its victims. Before the introduction of penicillin in 1943, syphilis was a common killer. In 1929, among men, the death rate from syphilis was 28.3 per 100,000 for Whites and 97.9 per 100,000 for Blacks . The similarities between syphilis and dementia were addressed repeatedly in the early literature in Alzheimer’s disease . Because syphilis can now be treated easily and cheaply, it has nearly been eradicated. But there is a new bacterium threat emerging—one that also causes dementia.
Today, the main bacterial threat to cause dementia comes from Lyme disease—a bacterium borrelia burgdorferi. Lye disease is transmitted to humans through the bite of infected blacklegged ticks. These ticks are themselves infected by feeding off infected insects and birds, which bring the infection from across the globe. Worldwide there are 23 different species of these Lyme disease ticks.
Lyme disease is the most common disease transmitted by animals in the northern hemisphere and it is becoming an increasingly public health concern . Not only because Lyme disease is a debilitating disease, but because eventually Lyme disease has been shown to cause dementia—Lyme dementia . Science has not identified the mechanism for the development of Lyme dementia but more than 65 countries have the blacklegged ticks which transmit Lyme disease.
Ernie Murakami, a retired physician who has been monitoring the spread of Lyme disease in the north and south of the 49th parallel. The prevalence varies dramatically. Canada reporting the lowest cases in the world, with 1 case per million, while the Slovenia reports 13 cases per 10,000. In the United Sates the Centers for Disease Control and Prevention reports that more than 329,000 people are likely to be infected every year in the U.S. alone. Only one in ten cases are reported since clinicians are not looking for it. This estimated number of infections is higher than hepatitis C, HIV, colon cancer, and breast cancer. Lyme disease accounts for more than 90% of all reported cases of diseases transmitted by animals (vector-borne illness).
With any good public health strategy there needs to be a two pronged reaction. One is to address the clinical effects of the disease and the other is to address the underlying cause. In the United States, although research funds to examine and explore cures for Lyme disease are minimal, this avenue is likely to see the most significant increase. But this would be folly without addressing the underlying cause of the disease. Addressing these underlying causes will be a challenge.
A Harvard Medical School Center reports that areas suitable for tick habitation will quadruple by the 2080s. But there are more pressing changes that will happen in our lifetime. Deforestation and climate-induced habitat change are affecting insects, which carry disease like malaria and Lyme disease. Slow climate change, urban growth in areas next to forests, reforestation following the abandonment of agriculture, and the increase in the deer population which harbor these ticks are increasing .
Malaria and Lyme disease are both projected to increase. One to the north and south of the 49 parallel while malaria will increase in the geography in the middle ground. Even taking a more conservative estimate (all of the USA, most of Canada, all of Europe, Middle East and China), there are more than half the world’s populations that are vulnerable to Lyme disease. A proportion of these populations will become infected with Lyme disease and eventually lead to dementia. Is public health ready to address this?
© USA Copyrighted 2017 Mario D. Garrett
© USA Copyrighted 2017 Mario D. Garrett
 Garrett MD (2015) Politics of Anguish: How Alzheimer's disease became the malady of the 21st century. Createspace. USA.
 Hazen H.H. (1937). A leading cause of death among Negroes: Syphilis. Journal of Negro Education, 310-321.
 Pearson S. (2014). Recognising and understanding Lyme disease. Nursing Standard, 29(1): 37-43.
 Blanc F., Philippi N., Cretin B., Kleitz C., Berly L., Jung B., ... & de Seze J. (2014). Lyme Neuroborreliosis and Dementia. Journal of Alzheimer's Disease, 41(4): 1087-93.