Colonization of Lutzomyia verrucarum and Lutzomyia longipalpis Sand Flies (Diptera: Psychodidae) by Bartonella bacilliformis, the Etiologic Agent of Carrión’s Disease

Abstract

Bartonella bacilliformis is a pathogenic bacterium transmitted to humans presumably by bites of phlebotomine sand flies, infection with which results in a bi-phasic syndrome termed Carrión’s disease. After constructing a low-passage GFP-labeled strain of B. bacilliformis, we artificially infected Lutzomyia verrucarum and L. longipalpis populations, and subsequently monitored colonization of sand flies by fluorescence microscopy. Initially, colonization of the two fly species was indistinguishable, with bacteria exhibiting a high degree of motility, yet still confined to the abdominal midgut. After 48h, B. bacilliformis transitioned from bacillus-shape to a non-motile, small coccoid form and appeared to be digested along with the blood meal in both fly species. Differences in colonization patterns became evident at 72h when B. bacilliformis was observed at relatively high density outside the peritrophic membrane in the lumen of the midgut in L. verrucarum, but colonization of L. longipalpis was limited to the blood meal within the intra-peritrophic space of the abdominal midgut, and the majority of bacteria were digested along with the blood meal by day 7. The viability of B. bacilliformis in L. longipalpis was assessed by artificially infecting, homogenizing, and plating for determination of colony-forming units in individual flies over a 13-d time course. Bacteria remained viable at relatively high density for approximately seven days, suggesting that L. longipalpis could potentially serve as a vector. The capacity of L. longipalpis to transmit viable B. bacilliformis from infected to uninfected meals was analyzed via interrupted feeds. No viable bacteria were retrieved from uninfected blood meals in these experiments. This study provides significant information toward understanding colonization of sand flies by B. bacilliformis and also demonstrates the utility of L. longipalpis as a user-friendly, live-vector model system for studying this severely neglected tropical disease.

First Report of Bartonella SP. In Sand Flies (Diptera: Psychodidae: Phlebotominae) From Southern Mexico

“…The genus Bartonella encompasses more than 33 species of Gram-negative, facultative intracellular and hemotropic bacteria, which can cause chronic intraerythrocytic infections in their mammalian hosts, especially rodents and humans (Chomel et al 2009). Several blood-feeding arthropods are involved in the transmission of these bacteria, such as fleas, sand flies, sucking lice, Acari, and other arthropods (Kosoy et al 2012, Kamani et al 2013, Battisti et al 2015, Regier et al 2016.…”

“…We cannot confirm whether sand flies are vectors of this bacterium in this area, since the arthropod could feed on blood meal from an infected host and not necessarily transmit the microorganism. It is possible that other lineages of Bartonella (pathogenic or nonpathogenic) can circulate in the fauna from Veracruz, yet the range of vectors involved in the transmission of Bartonella species remains to be established (Maroli et al 2013, Battisti et al 2015.…”

Carrion's Disease: the Sound of Silence

“…After oviposition and the death of the insects, PCR was performed to detect the microorganism. The results showed that insects fed blood with a higher bacteremia had a shorter life, and most of the infected females (35 out of 36) were unable to perform oviposition, while no Bartonella-positive descendant of the remaining infected female was obtained, supporting the hypothesis of a higher mortality of L. verrucarum in the presence of higher bacteremia and the absence of vertical (223). Unfortunately, analysis of feces or diuretic body fluids was not carried out in the L. verrucarum group.…”

“…Thus, L. longipalpis eliminates B. bacilliformis, while bacteria in L. verrucarum survive on blood meal digestion, colonizing the entire digestive tract of the sand fly(223). Although sporadic transmission of Carrion's disease related to L. longipalpis cannot be ruled out because the microorganism remains viable within L. longipalpis for up to 11 days, no mechanical transmission or isolation of viable B. bacilliformis has been obtained from feces or diuretic body fluids(223). B. bacilliformis was not observed in feces or diuretic body fluids of L. longipalpis or in eggs of L. verrucarum and L. longipalpis…”

Novel small RNAs expressed byBartonella bacilliformisunder multiple conditions reveal potential mechanisms for persistence in the sand fly vector and human host

“…B. bacilliformis is transmitted between humans through the bite of female phlebotomine sand flies, specifically Lutzomyia spp. [4,5]. The endemic region of Carrión's disease has historically been limited to arid, high-altitude valleys (600 -3200m) in the Andes Mountains of Peru, Colombia, and Ecuador, reflecting the habitat of the sand fly vector [6,7].…”