Caused by the spirochete Borrelia burgdoeri, Lyme disease is the most commonly reported vectorborne illness in the United States (Centers for Disease Control and Prevention, 2017c). Lyme borreliosis follows tick bites of the genus Ixodes. There are three stages (Steere, 2015). Early infection-stage I-causes a distinctive local skin lesion, erythema migrans, which may be accompanied by a flulike syndrome and regional adenopathy. If untreated, disseminated infection-stage 2-follows in days to weeks. Multisystem involvement is frequent, but skin lesions, arthralgia, myalgia, carditis, and meningitis predominate. If still untreated after several weeks to months, late or persistent infection-stage 3-manifests in perhaps half of patients. Native immunity is acquired, and the disease enters a chronic phase in about 10 percent. Some patients remain asymptomatic, but others in the chronic phase develop various skin, joint, or neurological manifestations (Shapiro, 2014).
Clinical diagnosis is important because serological and PCR testing has many pitfalls (Steere, 2015). IgM and IgG serological testing is recommended in early infection and is followed by Western blotting for conirmation. Ideally, acute and convalescent serological evaluation is completed if possible, however, false-positive and -negative rates are high.
Optimal treatment of Lyme disease was published by the Infectious Diseases Society of America (Sanchez, 2016). For early infection, treatment with doxycycline, amoxicillin, or cefuroxime is recommended for 14 days, although doxycycline is usually avoided in pregnancy. A 14-to 28-day course of IV ceftriaxone, cefotaxime, or penicillin G is given for complicated early infections that include meningitis, carditis, or disseminated infections. Chronic arthritis and post-Lyme disease syndrome are treated with prolonged oral or IV regimens, however, symptoms respond poorly to treatment (Steere, 2015).
No vaccine is commercially available. Avoiding areas with endemic Lyme disease and improving tick control in those areas is the most efective prevention. Self-examination with removal of unengorged ticks within 36 hours of attachment reduces infection risk (Hayes, 2003). For tick bites recognized within 72 hours, a single 200-mg oral dose of doxycycline may reduce infection development.
Several reports describe Lyme disease in pregnancy, although large series are lacking. Transplacental transmission has been confirmed, but no congenital efects of maternal borreliosis have been conclusively identiied (Shapiro, 2014; Walsh, 2006). Prompt treatment of maternal early infection should prevent most adverse pregnancy outcomes (Mylonas, 201l).
Diagnosis and management of tuberculosis during pregnancy is discussed in detail in Chapter 51 (p. 995).
The obligate intracellular parasite Toxoplasma gondii has a life cycle with two distinct stages (Kim, 2015). he eline stage takes place in the cat-the deinitive host-and its prey. Unsporu lated oocysts are excreted in feces. In the non eline stage, tissue cysts containing bradyzoites or oocysts are ingested by the inter mediate host, including humans. Gastric acid digests the cysts to release bradyzoites, which infect small-intestinal epithelium.
Here, they are transformed into rapidly dividing tachyzoites, which can infect all cells within the host mammal. Humoral and cell-mediated immune defenses eliminate most of these, but tissue cysts develop. Their lifelong persistence is the chronic form of toxoplasmosis.