A patient, handsome and slim, only 39yo complains headache and progressive memory loss. He is a cat lover and love to show us the photos of his dear cats. Since he caught AIDS and his partner left him, he adopted 8 cats and love them dearly as his own families. However, recently, he cannot remember or mess up his lovely cats' names and always forget whether he had fed them or not , sometimes even had bad headache attack. His brain CT scan show multiple ringed lesions and I reviewed his brain lesion biopsy specimen. Multiple tiny cysts contains schools of bradyzoids and uncysted tachyzoids is freely swimming and damaging the surrounding brain tissue. Ok, the diagnosis is clear, brain toxoplasmosis (toxoplasmic enchephalitis). Follow-up serology test is positive for IgG antibody to Toxoplasma gondii .
Toxoplasmosis is an infection by an parasite, Toxoplasma gondii (T. gondii for short from now on), which is most often finds in the house cat. Transmit by oral route. when your immune system is strong, T.gondii is hiding inside the cyst, called bradyzoids ( brady-means slow). The cyst is formed by our own cell membrane. Definetely, our immune system won't attack our own cell component. When your immune system is weak, like AIDS, on chemotherapy, or seniors, the T. gondii will step out of his camouflage cyst and called tachyzoids (tachy-means fast) and quickly spread to blood, brain, skeletal muscle and eye, and lead to severe consequences. So far, this parasite is really smart, 頗諳《孫子兵法>>. when you are strong, he slows down and hiding, when u r weak, he will flare and fight back.
Toxoplasmosis is considered to be a leading cause of death attributed to foodborne illness in the United States. Since cat is a so popular pet world widely, and toxoplasmosis is transmitted mainly by consuming food or water contaminated with cat feces. Toxoplasmosis is becoming a global health hazard as it infects 30-50% of the world human population, approximately in every two to three persons will have one with latent infection. More than 60 million men, women, and children in the U.S. carry the Toxoplasma parasite.
It may be overly generous to say that the parasite toxoplasma gondii has not received much coverage in the popular press. In fact, discussion over this parasite is almost exclusively limited to scientific literature.
Clinically, the life-long presence of the parasite in tissues of a majority of infected individuals is usually considered asymptomatic. However, a number of studies show that this 'asymptomatic infection' may also lead to development of other human diseases.
1. T. gondii infection appears to affect cognition in humans,considering diseases such as dementias and Alzheimer’s, it is not a mystery that areas of higher-order thinking (primarily memory centers) in the human brain are more susceptible to insult from foreign bodies.
2. infection with T. gondii has been associated with mood disorders, like Major Depressive Disorder (MDD), General Anxiety Disorder (GAD), or Panic Disorder (PD).
3.T. gondii has been associated with schizophrenia, bipolar disorder, parkinson’s disease and many others.
4. Behavioural changes persist after toxoplasma infection is cleared. Animal tests of mice infected with toxoplasmosis lose their instinctive fear for cats.
If you are interested in how to prevent and control of toxoplasmosis,here is the link on CDC:
http://www.cdc.gov/parasites/toxoplasmosis/prevent.html
REFERENCES
Barford E. Parasite makes mice lose fear of cats permanently. Nature .2013.13777
Flegr, J. 2010. Influence of latent toxoplasmosis on the phenotype of intermediate hosts. Folia Parasitol (Praha), 57, 81-87.
Flegr, J. 2013. Influence of latent Toxoplasma infection on human personality, physiology and morphology: pros and cons of the Toxoplasma-human model in studying the manipulation hypothesis. J Exp Biol, 216, 127-133.
Gale, S. D., Brown, B., Berrett, A., Erickson, L. D., & Hedges, D. W. Association between latent toxoplasmosis and major depression, generalized anxiety disorder and panic disorder in human adults. Folia Parasitol. 61(4): 285-292.
Gale, S. D., Brown, B., Erickson, L. D., Berrett, A., & Hedges, D. W. (In press). Association between Latent Toxoplasmosis and Cognition in Adults: A Cross-Sectional Study. Parasitology.
Henriquez, S. A., Brett, R., Alexander, J., Pratt, J. & Roberts, C. W. 2009. Neuropsychiatric disease and Toxoplasma gondii infection. Neuroimmunomodulation, 16, 122-33.
