**3.4 Clinical presentations of** *C. trachomatis* **in children**

*C. trachomatis* infects non-ciliated squamocolumnar or transitional epithelial cells that are susceptible (e.g., mucous membranes of the conjunctivae, posterior nasopharynx, urethra, endocervix, and rectum).

#### *3.4.1 Perinatal infection*

Typically, a newborn acquires an infection while passing through an infected birth canal, but it is known that transmission via cesarean delivery is possible, whether or not the membranes rupture prematurely. The prevalence of *C. trachomatis* infection in pregnant women varies depending on the population studied, ranging from 2 to 20% [52–54]. As in the general population, young women, particularly adolescents, had the highest prevalence of infection during pregnancy. In a British study of 1216

pregnant women, the overall CT infection prevalence was 2.4%, but it increased to 8.6% under the age of 25 years and 14.3% in the adolescent group [55]. Another study found that 18% of 203 pregnant adolescents had *C. trachomatis* infection in the third trimester of pregnancy [56].

The conclusion of many studies done in the 1980s was that maternal carriage of *C. trachomatis* is associated with a high incidence of clinical illness in infants. Prospective studies of infants born to mothers with chlamydial infection of the cervix have revealed a 50–75% risk of *C. trachomatis* acquisition in at least one anatomic site, including the conjunctiva, nasopharynx, rectum, and vagina [57]. Infants exposed to untreated *C. trachomatis* are estimated to have a 20–50% risk of conjunctivitis and a 5–20% risk of pneumonia [57–59]. In a recent Chinese study, the vertical transmission rate was determined to be 67% after vaginal delivery and 8% after a cesarean section [60]. Symptomatic chlamydia appears in infants mostly between the ages of 4 and 5 weeks, with a range of 2–20 weeks [56, 61].

#### *3.4.1.1 Inclusion conjunctivitis*

*C. trachomatis* has been reported to be the *most prevalent cause* of ophthalmia neonatorum in many countries and neonatal conjunctivitis is the *primary clinical manifestation* of chlamydial infection in neonates [62–64]. The findings of studies conducted in various countries clearly show that the distribution of key etiological agents of newborn conjunctivitis corresponds to the real prevalence of STI infections among pregnant women.

Ocular findings start usually between 5 and 14 days postpartum, although they can occur earlier if a premature membrane rupture is present. Mucopurulent discharge (95%), swelling of the eyelids (73%), and conjunctival erythema (65%) are the defined symptoms [65]. The vast majority of cases resolve spontaneously, but conjunctivitis can be long-lasting and severe; in the condition of severe inflammation, a pseudomembrane formation develops as a result of large exudates adhering to the conjunctivae. Conjunctivae may bleed during the examination or sampling. Corneal ulceration, scarring, and pannus formation are uncommon; and recovery without visual impairment is expected. Bloodstained eye discharge was found to have high specificity and positive predictive value for chlamydial conjunctivitis in a retrospective study of 90 infants from Hong Kong with chlamydial conjunctivitis [66]. At least 50% of infants with chlamydial conjunctivitis also have a nasopharyngeal infection, and 50% of the pneumonia cases have evidence of previous conjunctivitis [56, 67].

Neonatal prophylaxis with antibiotic-containing ointments has no effect on the incidence of chlamydial conjunctivitis or the development of nasopharyngeal carriage and pneumonia [68, 69].

Differential diagnosis of gonococcal and other pyogenic conjunctivitis is not possible based on clinical findings, but ophthalmia neonatorum due to gonococcal infection usually begins earlier (postnatal 3–5 days).

### *3.4.1.2 Neonatal pneumonia*

The importance of *C trachomatis* as a causal pathogen for respiratory illness in young infants is well documented in the literature [62]. *C. trachomatis* seems the etiological agent of 7–30% of the hospitalized pneumonia cases before 6 months of age [70–74].

Clinical manifestations of chlamydial pneumonia typically appear between the ages of 3 and 12 weeks. The majority of the infants are only mildly ill and afebrile. Nasal obstruction and *staccato* cough worsen over one or more weeks. Tachypnea and rallies are found on physical examination, but wheezing is uncommon. An X-ray of the chest will usually show hyper aeration as well as bilateral interstitial infiltration. Peripheral eosinophilia (>400 cells/mm3 ) is a distinctive laboratory finding but the total white cell number is usually normal [73, 75]. Concomitant or history of conjunctivitis is present in 30–50% of cases. The absence of fever and significant wheezing may be useful in the differential diagnosis of RSV infection, which is the most common pathogen in this age group.

Infected preterm neonates, may present differently. They can be symptomatic as early as 48 hours after birth, manifesting as idiopathic respiratory distress syndrome, which improved initially but was complicated by apneic spells and feeding difficulties [76]. Severe infections causing respiratory failure are also defined in the literature [77–79].

#### *3.4.1.3 Infections at other sites*

It is possible to detect asymptomatic rectal or vaginal *C. trachomatis* in 14% of neonates born to women with chlamydial infection, which can persist for 18 months [80, 81]. The presence of *C. trachomatis* in the genital tract can complicate the evaluation of probable sexual abuse and necessitates a thorough investigation [81].

#### *3.4.2 Infections in older children*

No specific clinical syndrome has been associated with *C. trachomatis* in older infants and children. The majority of focus on *C. trachomatis* infection in these children has centered on its association with child sexual abuse. As mentioned previously, perinatal maternal–infant transmission resulting in vaginal and/or rectal infection has been documented with up to three years of prolonged infection.

If *C. trachomatis* established in a prepubertal child from a rectal or genital site, sexual abuse must always be considered and a detailed multidisciplinary assessment of sexual abuse should be performed [82]. There is no evidence in the literature about the transmission of this organism without sexual activity such as via fomites.

#### *3.4.3 Infections in adolescents*
