Major
Biology
Research Abstract
Schistosomiasis is a parasitic disease that infects 200 million individuals, in mainly undeveloped countries, killing thousands. Schistosoma mansoni is one causative parasite, and it is transmitted by the freshwater snail Biomphalaria glabrata. B. glabrata snails of the BS-90 strain have shown neonatal susceptibility to the parasite, while adults are resistant, although the mechanism is unknown. Here we show that resistance to the parasite may be a function of snail size, since prevalence of infection is lower in larger snails, and since larval parasites (sporocysts) in larger snails have fewer germinal cells, are surrounded by a multilayered capsule of hemocytes, and elicit a strong mitotic response in the snail’s immune tissue. A lower germinal cell count in a sporocyst indicates that the parasite is in an unhealthy physiological state, inasmuch as these are reproductive cells. Additionally, encapsulation signifies that a host response is occurring, as hemocytes surround and constrict the sporocyst. Furthermore, the increase of mitotic figures in the snail immune tissue also suggests a stronger response against the infection in larger snails. Our results demonstrate that snails may develop a more robust immune system as they grow, thereby becoming resistant to infection. Subsequent studies could test for changes in gene expression as a function of size to better understand the mechanism underlying our findings.
Faculty Mentor/Advisor
Dr. John T Sullivan
Included in
Size Resistance to Infection with the Schistosome Parasite in the Vector Snail
Schistosomiasis is a parasitic disease that infects 200 million individuals, in mainly undeveloped countries, killing thousands. Schistosoma mansoni is one causative parasite, and it is transmitted by the freshwater snail Biomphalaria glabrata. B. glabrata snails of the BS-90 strain have shown neonatal susceptibility to the parasite, while adults are resistant, although the mechanism is unknown. Here we show that resistance to the parasite may be a function of snail size, since prevalence of infection is lower in larger snails, and since larval parasites (sporocysts) in larger snails have fewer germinal cells, are surrounded by a multilayered capsule of hemocytes, and elicit a strong mitotic response in the snail’s immune tissue. A lower germinal cell count in a sporocyst indicates that the parasite is in an unhealthy physiological state, inasmuch as these are reproductive cells. Additionally, encapsulation signifies that a host response is occurring, as hemocytes surround and constrict the sporocyst. Furthermore, the increase of mitotic figures in the snail immune tissue also suggests a stronger response against the infection in larger snails. Our results demonstrate that snails may develop a more robust immune system as they grow, thereby becoming resistant to infection. Subsequent studies could test for changes in gene expression as a function of size to better understand the mechanism underlying our findings.
