Lichtenstein and Brug first recogni

Lichtenstein and Brug first recognized B. malayi as a distinct pathogen in 1927. They reported the occurrence of a species of human filariae in North Sumatra that was both physiologically and morphologically distinct from the W. bancrofti microfilariae commonly found in Jakarta and named the pathogen Filaria malayi.[2] However, despite epidemiological studies identifying Filaria malayi in India, Sri Lanka, China, North Vietnam, and Malaysia in the 1930s, Lichtenstein and Brug’s hypothesis was not accepted until the 1940s, when Rao and Mapelstone identified two adult worms in India.[3]

Based on the similarities with W. bancrofti, Rao and Mapelstone proposed to call the parasite Wuchereria malayi[2] In 1960, however, Buckley proposed to divide the old genus Wuchereria, into two genera, Wuchereria and Brugia and renamed Filaria malayi as Brugia malayi. Wuchereria contains W. bancrofti, which so far has only been found to infect humans, and the Brugia genus contains B. malayi, which infects humans and animals, as well as other zoonotic species.[4]

In 1957, two subspecies of human infecting B. malayi were discovered by Turner and Edeson in Malaysia based on the observation of different patterns of microfilaria periodicity.[2] Periodicity refers to a pronounced peak in microfilariae count during a 24‑hour interval when microfilariae are present and detectable in the circulating blood.[4] The basis for this phenomenon remains largely unknown.[5]

Nocturnal periodicity: microfilariae are not detectable in the blood for the majority of the day, but the microfilarial density peaks between midnight and 2 AM nightly.
Nocturnal subperiodicity: microfilariae are present in the blood at all times, but appear at greatest density between noon and 8 PM.[4]