Worldwide, two billion people are infected with helminth infections. Helminths – including roundworms and flatworms – cause diseases that not only cripple and kill people, but cost many lower-income societies their chances of having a better community.
Helminths are split into two categories of parasitic families: roundworms (Nematoda) and flatworms (Platyhelminthes). Helminths are the most common infection in developing countries, and can cause symptoms from enlarged limbs to complications when interacting with the AIDS/HIV virus.
Unlike smaller agents, like tuberculosis and influenza, helminths are harder to study because of their complex genomes and large size.
Although helminths have been a scourge for thousands of years, it is only recently that they have begun to become ubiquitous due to various geo-political changes. For example, the construction of dams and waterways in African countries creates new environments for helminths to grow and develop. Worms have also found their way into the hilly and mountainous regions of China. In addition, new species of helminths that are combination of human and cattle worms are popping up globally.
This article, by Paul Bridley, explores the connection between the genomics of the parasitic infection and how the helminths themselves reproduce and feed. This study will help improve treatment options and our understanding of the problem that plagues communities worldwide.
Using technology such as RNA interference and transgenesis, we learn how the body, the immune system, and specifically how T cells work to fight back the infection. From this research, we can now develop new drugs, treatments, and programs to treat a helminth infestation.
Many of the difficulties surrounding researching the genome of helminths comes from life cycle complications, tissue complexity, and the difficult to handle genetic material.
The first helminth successfully genomed was the roundworm C. elegans, and was completed in 1998. It is still currently the only helminth that we have a high confidence of every nucleotide. In 22 other gene sequences of helminths we have discovered today, and are either partially or fully completed. Researches use comparative genome analysis in order to effectively sequence the genome of these helminths by comparing their DNA to those of the hosts that they infect. For example, comparative genome analysis has been used to link B. Malayi with Wolbachia.
The genomes sequenced of both S. japonicum and S. mansoni – both members of Lophotrochozoa – reveal an important clue to deciphering the host-parasite relationship. While members of Lophotrochozoa usually have around 6000 protein families, both of these helminths abandoned approximately 1000 of these protein families, which are important for both metabolism and defence. This being known, the some of other 5000-some protein families must be key towards the helminth developing parasitic behavior and tendencies, such as burrowing into the feet or moving up the human body.
Regulatory networks in embryonic development, development, and reproduction of helminths show that there are certain signaling pathways in the human body that helminths can use to regulate their growth. In a sense, the worms use human growth hormones as their own growth hormones.
Helminths can change the immune response in order to increase their chances of survival. For example, after entering the human body helminths suppress, divert, and alter the host’s response, and create an anti-inflammatory environment in which to grow. They do this by interfering with the cytokine network and inhibiting enzymes from completing their projects. Depending on where and how the helminth enters the body, the subversion of the immune system is done through different secretions.
An infection by a helminth can compromise the entire immune system of the host. Because of this, helminths have been studied in their possibility to act as a cure to allergies and autoimmune diseases present in the human body like Crohn’s disease and ulcerative chloritis. Secretions by certain helminths have been tested in treating sensitive skin and arthritis. Because the helminths interact with mast cells and the release of signaling molecules, they can keep inflammation from these autoimmune diseases to a minimum.