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Pathogens and Disease

Intestinal nematode parasites: mechanisms of resistance

Intestinal nematode parasites are very common infections of man and his domestic animals. When the host becomes infected, often by oral ingestion of infective eggs, the parasite establishes in its intestinal niche. Parasite antigens are carried by intestinal dendritic cells, or drain freely in the lymph, to the local draining lymph node, the mesenteric lymph node. In the mesenteric lymph node antigen is presented to T cells in the context of MHC class II.

Pathogenic Yersiniae

Pathogenic bacteria of the Yersinia genus cause three types of disease, namely: plague (Yersinia pestis; Figure 1), pseudotuberculosis (Yersinia pseudotuberculosis) and yersiniosis (Yersinia enterocolitica). In achieving this, these pathogens exhibit common ways of manipulating the mammalian host‘s immune system to achieve their own survival (see related articles).

Pseudotuberculosis

Pseudotuberculosis, caused by Yersinia pseudotuberculosis, is a zoonosis which can be transmitted to man through skin contact with infected animals, contaminated water, or by the consumption of contaminated food or vegetables.

Respiratory Syncytial Virus (RSV)

Respiratory Syncytial Virus (RSV) is a major cause of disease in childhood and old age, with symptoms ranging from a common cold to bronchiolitis and pneumonia. An estimated 160,000 – 200,000 deaths globally can be attributed to RSV infection. The burden on healthcare infrastructures is significant, and in the U.S. it is estimated to cost $600 million per year. Even though most children are exposed to RSV within the first two years of life, lifelong re-infection with RSV is common, even within the same season and sometimes with the same strain.

Malaria

With an estimated 216 million cases annually among 3.3 billion people at risk, malaria is a leading cause of death and disease worldwide, particularly affecting children under 5 and pregnant women. More than 90% of the disease burden is in sub-Saharan Africa where climate conditions are favourable for the mosquito vector to thrive, but malaria continues to cause considerable morbidity in Asia and south America.

Microbial infection in cystic fibrosis

Cystic fibrosis (CF) is the UK’s most common inherited disease affecting around 1 in 2,500 births (predominantly affecting Caucasians). It is an autosomal recessive disease, i.e. the faulty gene occurs on an autosomal chromosome and two copies of the defective gene are required to develop the condition. In the UK, around 2 million people are carriers and although they do not have the disease, two carriers have a 1 in 4 chance of having a child with CF.

Tuberculosis

Tuberculosis (TB) in humans is caused by infection with Mycobacterium tuberculosis, which is a non-motile, slow-growing, rod-shaped bacillus. Current figures from the World Health Organisation estimate 8.8 million people developed active TB disease globally in 2010, leading to approximately 1.45 million deaths as a result of the infection.

Ulcerative colitis and Trichuris infection

Inflammatory bowel disease (IBD) comprises a group of idiopathic chronic relapsing inflammatory conditions of the gastrointestinal tract. IBD commonly involves two conditions, ulcerative colitis and Crohn’s disease. Ulcerative colitis mainly affects the colon, whereas Crohn’s disease can involve any part of the intestine. IBD may present as abdominal pain, diarrhoea, rectal bleeding, strictures and fibrosis. The precise aetiology for both the diseases is unknown.

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