Seroprevalence and risk factors for infection with Bartonella bacilliformis in Loja province, Ecuador

Figures & data

Overall demographics and individual responses to entomological questions of surveyed children in the six communities in Loja province, Ecuador (EC)

	n	%
Gender
Male	166	52.2
Female	153	47.8
Age categories, years
1–5	112	35.1
6–10	119	37.3
11–15	88	27.6
Travel^a
None or within Loja province	256	82.6
Non-endemic provinces in EC	17	5.5
Endemic provinces in EC or Peru	26	8.4
Destination not stated	11	3.5
Recognize sand flies^b
Yes	168	57.1
No	126	42.9
Bitten by sand flies
Yes	261	85.9
No	43	14.1

Community	# Houses	House elevations average MASL^c	# Children per age group
			1–5	6–10	11–15
Jacapo	27	1667	25	35	28
Usaime	26	1574	17	20	17
Galapagos	22	1268	22	20	18
Santa Rosa	14	1476	11	9	6
Vega del Carmen	20	1156	22	18	9
Chirimoyos	19	1112	14	18	10

^aIn Ecuador, non-endemic provinces included El Oro, Azuay, Sucumbios, and Pichincha (no reported Carrion’s disease). Endemic provinces in EC included Manabi and Guayas (verruga peruana) and Piura, Peru (Oroya fever)

^bSand flies were identified from pictures

^cMeters above sea level (MASL)

Overall B. bacilliformis seropositivity in children by community and age group

	Antibody positive by age group					Antibody negative by age group
Community	1–5	6–10	11–15	Total	(%)^a	1–5	6–10	11–15	Total	(%)^a
Vega del Carmen	14^b	7	4	25	51%	8	11	5	24	49%
Chirimoyos	6	9	5	20	48%	8	9	5	22	52%
Santa Rosa	5	4	2	11	42%	6	5	4	15	58%
Usaime	6	6	8	20	36%	12	14	9	35	64%
Galapagos	3	3	1	7	12%	19	17	17	53	88%
Jacapo	3	4	1	7	8%	22	31	27	80	92%
Total # of children per age group in all communities	37	32	21	90		75	87	67	229
Total % Ab+ or Ab- children in all communities^c	33%	27%	24%	28%		67%	73%	76%	82%

Antibody was measured as IgG by rPap31 ELISA

^aPercentage of antibody-positive or antibody-negative children per community

^bNumber of children in each age category

^cPercentage of total antibody-positive or negative children by age group

Fig. 1 Age curve of seropositivity showing the percentage of children at each age from total children in all six study communities in Loja Province compared to the percentage of seropositive children at each age. The left axis corresponds to the line graph denoting the percentage of children at each age. The right axis corresponds to the bar graph denoting the percentage of children at each age that are seropositive

Comparison of seropositive children between communities by post hoc pairwise testing using Fisher’s exact tests of independence

Community (Ab+)	JP (7)	NGL (7)	NVC (25)	NVS (20)	SS (11)
CY (20)^a	< 0.0001^b	0.0009	1.0	1.0	1.0
JP (7)		1.0	0.0001	0.0018	0.002
NGL (7)			0.0001	0.0299	0.0219
NVC (25)				0.843	1.0
NVS (20)					1.0

CY Chirimoyes, JP Jacapo, NGL Galapagos, NVC Vega del Carmen, NVS Usaime, SS Santa Rosa

^aNumber of seropositive children

^bp < 0.0033 is significant at 95% CI (0.05 significance level/15 pairwise comparisons)

Household characteristics in the six study communities in Loja province

Households	n	%
Type of roof
Tile	106	92.2
Concrete	4	3.5
Zinc	3	2.6
Asbestos	1	0.9
Palm Straw	1	0.9
Type of walls
Adobe	110	86.1
Brick/concrete	17	13.0
Bamboo/paper lined	1	0.9
Type of floor
Dirt	83	72.2
Concrete/brick	25	21.7
Rough wood	6	5.2
Bamboo	1	0.9
Peridomestic animals
Dogs	102	89.5
Cats	72	63.2
Birds/Livestock
Chickens	110	95.6
Pigs/swine	95	83.3
Guinea pigs	51	44.3
Sheep/goats	31	27.1
Wild animals in/near house
Mice	97	84.3
Rats	100	88.7
Opossums/foxes	69	60.5
Materials near house
Firewood	87	76.3
Trash	79	68.7
Rocks/bricks	39	34.2
Lumber pile	16	14.0
Organic matter
Animal manure	42	36.8
Crop waste	37	32.2
Vegetation
Bushes	93	81.2
Weeds	83	72.8
Fruit trees	51	44.3
Agave	1	0.9

Univariate associations between B. bacilliformis seropositivity and select variables

Variable	Seropositive n (%)	Seronegative n (%)	OR (95% CI)	p
Recognize sand flies
Yes	56 (64.4)	113 (54.3)	1.52 (0.88–2.63)	0.122
No	31 (35.6)	95 (45.7)
Type of walls
Adobe	73 (91.2)	171 (82.2)	2.26 (0.74–6.87)	0.113
Brick/concrete	7 (8.8)	37 (17.8)
Guinea pigs
Yes	40 (49.4)	78 (37.5)	1.63 (0.87–3.02)	0.115
No	41 (50.6)	130 (62.5)
Sheep/goats
Yes	28 (34.2)	42 (20.1)	2.06 (1.06–4.01)	0.027^a
No	54 (65.8)	167 (79.9)
Rats
Yes	67 (81.7)	185 (89.4)	0.53 (0.24–1.19)	0.122
No	15 (18.3)	22 (10.6)
Animal waste
Yes	23 (28.0)	85 (40.7)	0.57 (0.30–1.09)	0.071
No	59 (72.0)	124 (59.3)
Lumber pile
Yes	15 (18.3)	21 (10.0)	2.00 (0.99–4.05)	0.052^a
No	67 (81.7)	188 (90.0)
Weeds
Yes	48 (59.3)	161 (77.0)	0.43 (0.22–0.55)	0.012^a
No	33 (40.7)	48 (23.0)
Elevation (m)^b,c	–	–	0.79 (0.70–0.89)	<0.001^a
Mean	1326 (n=89)	1448 (n=228)	–	<0.001^a

OR odds ratio, CI confidence interval

^aStatistically significant at p < 0.05. Odds ratio > 1.0 denotes increased risk

^bAs a variable, elevation is continuous and thus has no entries for number or % of seropositive/seronegative. However, a univariate odds ratio using logistic regression could still be calculated. The odds ratio is 0.79 for each 100 m of elevation and decreases for each 100 m increase in elevation

^cBecause elevation is continuous, we also calculated and compared the mean elevation for seropositives and seronegatives by Student’s t-test

Multivariate model 2 using logistic regression to determine associations between B. bacilliformis seropositivity including statistically significant variables from univariate analysis

Variable^a	Odds Ratio (95% CI)	p^b
Animal waste	0.47 (0.24, 0.91)	< 0.026
Lumber pile	2.47 (1.08, 5.63)	< 0.032
Elevation (per 100 m)^c	0.76 (0.66, 0.87)	< 0.001

OR odds ratio, CI  confidence interval

^aAnimal waste was also included for biological importance as a sand fly breeding site and larval food source

^bStatistically significant at p < 0.05

^cThe odds ratio is 0.76 for each 100 m of elevation; the odds ratio decreases for each 100 m increase in elevation. This is consistent with the univariate analysis

Fig. 2 Map of Ecuador (inset) with Loja province shaded.

The six study communities are identified in the large map of Loja province. Also shown is the provincial capital city of Loja and major communities of Catacocha (Paltas County) and Cariamanga (Calvas County). WGS84 coordinates for each community are as follows: Chirimoyos (04.12972°S, 79.5456°W), Vega del Carmen (04.10610°S, 79.59012°W), Jacapo (04.36621°S, 79.4162°W), Usaime (04.46035°S, 79.54414°W), Santa Rosa (04.3960°S, 79.41861°W, and Galapagos (04.35233°S, 79.4344°W)