This may be because of the inability of these agents to remove sufficient amounts of lead from tissue or inability to reverse preexisting damage. Chelating agents can have adverse effects; for example, chelation therapy can lower the bodys levels of necessary nutrients like zinc. Chelating agents taken orally can increase the bodys absorption of lead through the intestine.Chelation challenge, also known as provocation testing, is used to indicate an elevated and mobilizable body burden of heavy metals including lead. This testing involves collecting urine before and after administering a one-off dose of chelating agent to mobilize heavy metals into the urine. Then urine is analyzed by a laboratory for levels of heavy metals; from this analysis overall body burden is inferred. Chelation challenge mainly measures the burden of lead in soft tissues, though whether it accurately reflects long-term exposure or the amount of lead stored in bone remains controversial. Although the technique has been used to determine whether chelation therapy is indicated and to diagnose heavy metal exposure, some evidence does not support these uses as blood levels after chelation are not comparable to the reference range typically used to diagnose heavy metal poisoning. The single chelation dose could also redistribute the heavy metals to more sensitive areas such as central nervous system tissue. Epidemiology
Since lead has been used widely for centuries, the effects of exposure are worldwide. Environmental lead is ubiquitous, and everyone has some measurable blood lead level.
However, fleas serve as a vector for transmission of B. henselae among cats, and viable B. henselae are excreted in the feces of Ctenocephalides felis, the cat flea. Cats could be infected with B. henselae through intradermal inoculation using flea feces containing B. henselae.As a consequence, a likely means of transmission of B. henselae from cats to humans may be inoculation with flea feces containing B. henselae through a contaminated cat scratch wound or by cat saliva transmitted in a bite. Ticks can also act as vectors and occasionally transmit the bacteria to humans. Combined clinical and PCR-based research has shown that other organisms can transmit Bartonella, including spiders. Cryptic Bartonella infection may be a much larger problem than previously thought, constituting an unrecognized occupational health hazard of veterinarians. Diagnosis
The best diagnostic method available is polymerase chain reaction, which has a sensitivity of 43-76% and a specificity (in one study) of 100%. The Warthin–Starry stain can be helpful to show the presence of B. henselae, but is often difficult to interpret. B. henselae is difficult to culture and can take 2–6 weeks to incubate. Histology
Cat-scratch disease is characterized by granulomatous inflammation on histological examination of the lymph nodes. Under the microscope, the skin lesion demonstrates a circumscribed focus of necrosis, surrounded by histiocytes, often accompanied by multinucleated giant cells, lymphocytes, and eosinophils. The regional lymph nodes demonstrate follicular hyperplasia with central stellate necrosis with neutrophils, surrounded by palisading histiocytes (suppurative granulomas) and sinuses packed with monocytoid B cells, usually without perifollicular and intrafollicular epithelioid cells.