This is called Asthenozoospermia.
If there are white cells in the semen then there may be an infection. Sperm are particularly susceptible to damage from infection. Infection increases the amount of free oxygen radicals in seminal fluid, which affects sperm motility and function probably by a direct effect on the sperm membrane. Unlike other cells the sperm outer membrane is fairly tight around the genetic material in the nucleus. There is no fluid bathing this central area (called cytoplasm) which in other cells protects against free oxygen radicals.
White cells and immature sperm are often very difficult to distinguish so they are often unreported. Mild infection does not necessarily show with increased white cells and is sometimes due to mycoplasma species. These are fastidious organisms and difficult to grow. We therefore usually treat without sending a sample to try and grow the organisms as the attempt to grow them often fails.
Some men have increased white cells due to an immune response. Steroids are not effectual in improving fertility (although they may damp down the immune response) and have significant side effects in the dose required.
A Cox 2 anti-inflammatory (less effect on the stomach) for 30 days may help. There are some anxieties as to their long term effect on the heart and blood vessels. Ibuprofen might help but there are no supporting (or conflicting) studies.
If you have no symptoms then the infection may be in the prostate gland. Some men have no infection but just have high levels of free oxygen radicals in semen or alternatively low levels of the enzymes that normally combat the free oxygen radicals. This is an area of continuing research and as yet no conclusion has been reached.
Free oxygen radicals can be combated by antoxidants which occur both in vitamin supplimentation and naturally in certain fruits and vegetables.
If you have an infection however then stopping it is probably the only way to resolve the problem
Treatment is 2 pronged.
Firstly if an infection is suspected, we use an antibiotic. We use doxycycline as the organisms we suspect are usually sensitive to this tetracycline antibiotic and it only has to be taken once a day.
Secondly we advise an antoxidant. The commonest is Vitamin E- the dose seems to vary between 50 and 1000mgs although mostly it seems to run between 50 and 300mgs. Vitamin C 200-1000mgs can also be used. You should only use Vitamin E or C, given together seems to have an adverse affect (Hughes Human Reproduction 1998-13,1240). Vitamin C has also been shown to increase count in smokers (Dawson 1992 Fertility Sterility 58.1034). Vitamin E has been shown to increase motility in low motility samples.
Low glutathione levels lead to poor mobility; this is corrected usually with other antioxidants allowing the glutathione to recycle.
A number of infertility males seen to have a low intake of these.
A list of antioxidants