Oroya fever and verruga peruana: bartonelloses unique to South America

Abstract

Bartonella bacilliformis is the bacterial agent of Carrión's disease and is presumed to be transmitted between humans by phlebotomine sand flies. Carrión's disease is endemic to high-altitude valleys of the South American Andes, and the first reported outbreak (1871) resulted in over 4,000 casualties. Since then, numerous outbreaks have been documented in endemic regions, and over the last two decades, outbreaks have occurred at atypical elevations, strongly suggesting that the area of endemicity is expanding. Approximately 1.7 million South Americans are estimated to be at risk in an area covering roughly 145,000 km2 of Ecuador, Colombia, and Peru. Although disease manifestations vary, two disparate syndromes can occur independently or sequentially. The first, Oroya fever, occurs approximately 60 days following the bite of an infected sand fly, in which infection of nearly all erythrocytes results in an acute hemolytic anemia with attendant symptoms of fever, jaundice, and myalgia. This phase of Carrión's disease often includes secondary infections and is fatal in up to 88% of patients without antimicrobial intervention. The second syndrome, referred to as verruga peruana, describes the endothelial cell-derived, blood-filled tumors that develop on the surface of the skin. Verrugae are rarely fatal, but can bleed and scar the patient. Moreover, these persistently infected humans provide a reservoir for infecting sand flies and thus maintaining B. bacilliformis in nature. Here, we discuss the current state of knowledge regarding this life-threatening, neglected bacterial pathogen and review its host-cell parasitism, molecular pathogenesis, phylogeny, sand fly vectors, diagnostics, and prospects for control.

Figure 1. Clinical manifestations of Carrión's disease.

(A) Erythrocyte infection during OF, as observed in a blood smear stained with Wright's stain (reprinted by permission from [203]). (B) VP lesions on a child in Peru (reproduced from Future Microbiology 4(6): 743–758 (2009) with permission of Future Medicine, Ltd).

Figure 2. B. bacilliformis infection of a phlebotomine sand fly.

(A) Female L. verrucarum at 16 h post-feeding with an artificial blood feeder containing human blood and GFP-expressing B. bacilliformis (low-passage strains 14866 and 14868). (B) Light micrograph of L. verrucarum midgut at five days post-feeding on human blood containing GFP⁺ B. bacilliformis. Central brown area is residual blood meal. (C) Corresponding UV light micrograph of (B). Note the GFP⁺ B. bacilliformis in residual blood meal and elsewhere in the midgut.

Figure 3. Monthly sand fly collection results from three villages in the Cusco Region, Peru.

Results show a unimodal annual population distribution pattern with: (A) corresponding mean morning (blue line) and evening (pink line) temperatures and (B) corresponding mean morning (green line) and evening (red line) relative humidity. Collections were made during two nights per month at case homesteads from March 2001 to August 2004. The data gap between October 2001 and January 2002 is due to a cessation of activity mandated by the Peruvian Ministry of Health.

Figure 4. Results of collection-bottle-rotator (CBR) trap collections of sand flies in Peru.

Results show that: (A) nightly sand fly activity is limited to early evening (1800–2000 hrs) from March through July, the coldest part of the year, which represents the Peruvian winter, and (B) as nighttime temperatures increase in late August through November (late winter and spring), sand fly activity extends throughout the night. “Inside” and “outside” refer to trap locations within and outside a domicile, respectively.

Figure 5. Transmission electron micrographs showing morphology of B. bacilliformis.

Bacteria were grown three days on heart infusion agar containing 4% sheep erythrocytes and 2% sheep serum at 30°C and 100% relative humidity. Cells were subsequently fixed in 2% glutaraldehyde in cacodylate (pH 7.2), epoxy embedded by standard methods, then sectioned and stained with uranyl acetate (UA) and lead citrate stains. Micrographs show B. bacilliformis (strain KC583): (A) from a thin section; (B) applied directly to a grid stained with UA to show flagella. Scale bars represent 100 nm in (A) and 500 nm in (B).

Figure 6. Genomic structure of seven Bartonella chromosomes.

(A) Chromosomes (Chr) are arranged in size from largest (B. tribocorum) to smallest (B. bacilliformis). Plasmid (Pla) sizes are listed, if present. B. quintana's genome encodes the least number of proteins (1,142), and B. clarridgeiae has the lowest GC% (35.7%). Several virulence-related ORFs have been used to infer phylogeny (fla – vbh) and black circles indicate their presence in a particular species. (B) Multiple alignment of seven complete genomes using pM. Location, orientation and position of locally collinear syntenic blocks (LCBs) shared amongst all chromosomes are color-coded and connected by lines. User can analyze location, orientation, and size of LCBs in multiple chromosomes simultaneously (red arrowheads). Local rearrangements, duplications, and inversions are easily identified. Abbreviations correspond to the Bartonella species shown in (A).

Figure 7. Scanning electron micrographs of deformin-induced invaginations and pits on erythrocyte membranes.

B. bacilliformis colonization of cell membrane deformations is readily apparent. Reprinted by permission from .