Reservoir
Humans are the primary reservoir for Loa loa. Other minor potential reservoirs have been indicated in various fly-biting habit studies, such as hippopotamus, wild ruminants (e.g. buffalo), rodents and lizards. A simian type of loiasis exists in monkeys and apes but it is transmitted by Chrysops langi. There is no crossover between the human and simian types of the disease. A related fly, Chrysops langi, has been isolated as a vector of simian loiasis, but this variant hunts within the forest and has not as yet been associated with human infection. Vector
Loa loa is transmitted by several species of tabanid flies (Order: Diptera; Family: Tabanidae). Although horseflies of the genus Tabanus are often mentioned as vectors, the two most prominent vectors are from the tabanid genus Chrysops—C. silacea and C. dimidiata. These species exist only in Africa and are popularly known as deer flies and mango, or mangrove, flies.Chrysops spp. are small (5–20 mm long) with a large head and downward-pointing mouthparts. Their wings are clear or speckled brown. They are hematophagous and typically live in forested and muddy habitats like swamps, streams and reservoirs, and in rotting vegetation. Female mango and deer flies require a blood meal for production of a second batch of eggs. This batch is deposited near water, where the eggs hatch in 5–7 days. The larvae mature in water or soil, where they feed on organic material such as decaying animal and vegetable products. Fly larvae are 1–6 cm long and take 1–3 years to mature from egg to adult.
The dexamethasone suppression test (DST) is used to assess adrenal gland function by measuring how cortisol levels change in response to oral doses or an injection of dexamethasone. It is typically used to diagnose Cushings syndrome. The DST was historically used for diagnosing depression, but by 1988 it was considered to be "at best, severely limited in its clinical ability" for this purpose. Physiology
Dexamethasone is an exogenous steroid that provides negative feedback to the pituitary gland to suppress the secretion of adrenocorticotropic hormone (ACTH). Specifically, dexamethasone binds to glucocorticoid receptors in the anterior pituitary gland, which lie outside the blood-brain barrier, resulting in regulatory modulation. Test Procedures
There are several types of DST procedures:
Overnight DST - An oral dose of dexamethasone is given between 11pm and midnight, and the cortisol level is measured at 8 - 9am the next morning
Two-day DST - This involves giving an oral dose of dexamethasone at six-hourly intervals for 2 days, with the cortisol level measured 6 hours after the final dose was given
Intravenous DST
Dexamethasone-CRT test

Interpretation
Low-dose and high-dose variations of the test exist. The test is given at low (usually 1–2 mg) and high (8 mg) doses of dexamethasone, and the levels of cortisol are measured to obtain the results.A low dose of dexamethasone suppresses cortisol in individuals with no pathology in endogenous cortisol production. A high dose of dexamethasone exerts negative feedback on pituitary neoplastic ACTH-producing cells (Cushings disease), but not on ectopic ACTH-producing cells or adrenal adenoma (Cushings syndrome).