The PAM case described in this paper is the first to be reported in Zambia. This case was detected during one of the hot months with spiking temperatures supporting observations that N. fowleri infections are associated with hot seasonality . As has been reported elsewhere, the diagnosis of PAM possesses challenges in that its clinical presentation is similar to that of bacterial meningitis. Due to its rapid progression, death usually occurs within 6–17 days of initial exposure if not promptly diagnosed .
The lack of information on PAM in Zambia indicates that there is limited or no awareness among clinical and laboratory staff leading to misdiagnosis of cases. In the few cases of PAM successfully managed [10, 11] in other regions, correct and prompt diagnosis was done and treatment commenced without delay. In the absence of a detailed history of exposure, it is very difficult to clinically diagnose PAM as the infection presents like other types of meningitis. Our case presented with clinical signs and symptoms similar to those that have been previously documented [7, 12]. Symptoms such as severe headache, high grade fever, photophobia, lethargy, confusion with altered levels of consciousness and seizures are commonly observed in patients with PAM. Death in most of the cases is due to increased intracranial pressure .
Laboratory findings in PAM patients are consistent and are mostly characterized with increased leucocytes which are predominantly polymorphonuclear cells. CSF may also be purulent with marked leucocytosis, increased protein and reduced glucose levels [7, 12]. In most cases, neuro-imaging investigations in early stages of the disease do not reveal any brain abnormalities . However, a strong suspicion of PAM with history of water exposure should guide the management of patients with such presentations in the absence of bacteria or fungi in CSF specimens.
Critical to survival of PAM patients is prompt detection and aggressive treatment. Currently, the drug of choice is Amphotericin B, an antifungal agent with very low cure rate especially when used as a single drug . The sensitivity of Amphotericin B on N. fowleri was demonstrated as far back as the late 1960’s . Other drugs given alongside Amphotericin B are Rifampicin and Fluconazole. In cases where treatment has been successful, aggressive therapy with a combination of antibacterial and antifungal agents was given [8, 16]. Coupled with the use of the above mentioned drugs, management of intracranial pressure, inflammation and induced mild-moderate hypothermia (32 °C-34 °C) are key to successful recovery .
Even though the parasite is present in almost all the continents [6, 7], very few cases of PAM have been recorded since it was discovered in 1962. According to the centre for disease control and prevention (CDC), only 138 cases of PAM in the United States have been reported from 1962 to 2015. Recently, there has been an increase in the number of reported PAM cases in Asian countries [14, 17, 18] perhaps due to increased awareness.
In Africa, however, less than 10 cases have been recorded despite having weather conditions such as high temperature that favor the propagation of the parasite. The first reported case of PAM was in an 8 month old baby in Zaria state, Nigeria with no prior exposure to swimming . Following this case, another PAM patient was reported 2 years later in the same country . In addition, there is documentation of N. fowleri isolation from environmental sources [21,22,23]. N. fowleri has also been isolated from nasal passages during the dry, windy and dusty months (hamarrtan season) affecting parts of the West African coast . While most of the cases in Africa are from Nigeria, only one case has been documented in Southern Africa . The only case of suspected amoebic meningoencephalitis in a Zambian male gardener was reported in 1974 . In this case, the authors concluded that the infection was not as a result of Naegleria but rather another free living amoeba belonging to the hartmannellid family which has been classified as Acanthamoeba. It is conceivable therefore, to suggest that PAM cases are high in Africa and go undiagnosed due to lack of awareness among clinical and laboratory staff.