Detection of Rift Valley Fever virus inter-epidemic activity in Kilimanjaro Region, North Eastern Tanzania

Figures & data

Figure 1. Map of Tanzania showing the study site

Table 1. Demographic characteristics of human participants

Characteristics	n	%
Age group (years)
≤20	28	10.5
21–50	140	52.7
>50	98	36.8
(Median, IQR) years	45 (30–55)
Sex
Male	116	43.6
Female	150	56.4
Individuals living in a household
<4	68	25.6
≥4	198	74.4
Highest education
No formal education	51	19.2
School education (primary/secondary)	168	63.2
Tertiary education (college)	47	17.7
Type of animals kept by the participant
None	72	27.1
Chicken only	82	30.8
Goats and sheep only	54	20.3
Cattle only	55	20.7
Goats, sheep, cattle, and chicken	3	1.1
ITN use*
Yes	66	24.8
No	200	75.2

IQR, Interquartile range; *72 missing entries.

Table 2. Age, sex and number of herds of goat sampled (n = 2986)

Characteristics	n	%
Age category (months)
<12	1590	53.25
>12	1396	46.75
Sex
Male	899	30.1
Female	2087	69.9
Herd size*
<20	74	61.7
20–50	24	20.0
>50	22	18.3

*Total sampled herds = 120.

Table 3. Factors associated with RVFV seropositivity in humans

Variable	Level	Negative, n (%)	Positive, n (%)	χ^2(p)
Sex	Male	47 (34.3)	19 (55.9)
	Female	90 (65.7)	15 (44.1)	5.351 (0.030)
Age group	11–20	18 (13.1)	1 (2.9)
	21–30	26 (19.0)	2 (5.7)
	31–40	23 (16.8)	3 (8.6)
	41–50	19 (13.9)	4 (11.4)
	>50	51 (37.2)	25 (71.4)	14.430 (0.006)
Human RVFV PCR positivity	Positive	0 (0.0)	7 (20.0)
	Negative	1 (100.0)	28 (80.0)	0.248 (1.000)
ITN use	Yes	24 (17.9)	13 (37.1)
	No	110 (82.1)	22 (62.9)	6.003 (0.021)
Number of persons in a household	1–3	45 (33.1)	5 (14.3)
	4–6	74 (54.4)	13 (37.1)
	7+	17 (12.5)	17 (48.6)	23.213 (<0.001)
Travel outside site	Yes	48 (35.0)	10 (28.6)
	No	89 (65.0)	25 (71.4)	0.521 (0.551)
Destination of travel	Urban	22 (45.8)	3 (30.0)
	Peri-urban	10 (20.8)	1 (10.0)
	Rural	16 (33.3)	6 (60.0)	2.545 (0.346)
Highest education	No formal education	34 (24.8)	8 (22.9)
	School education (primary/secondary)	91 (66.4)	25 (71.4)
	Tertiary education (college)	12 (8.8)	2 (5.7)	0.465 (0.830)
RVFV PCR positivity in goats	Yes	2 (66.7)	8 (88.9)
	No	1 (33.3)	1 (11.1)	0.800 (1.000)
RVFV seropositivity in goats	Yes	106 (77.4)	11 (31.4)
	No	10,631 (22.6)	24 (68.6)	27.053 (<0.001)
Culex RVFV PCR positivity	Yes	1 (0.7)	33 (94.3)
	No	136 (99.3)	2 (5.7)	4.041 (0.106)
Aedes RVFV PCR positivity	Yes	0 (0.0)	2 (5.7)
	No	137 (100.0)	33 (94.3)	7.921 (0.04)
Type of animals kept	None	45 (80.40)	11 (19.60)
	Chicken	37 (78.70)	10 (21.30)
	Goats and sheep	29 (76.30)	9 (23.70)
	Cattle	25 (83.30)	5 (16.70)
	Goats, sheep, cattle	1 (100.00)	0 (0.00)	0.809 (0.929)

Table 4. Factors associated with RVFV seropositivity in goats

Variable	Level	Negative, n (%)	Positive, n (%)	χ2 (p)
RVFV PCR positivity in goats	Positive	3 (75.0)	8 (89.9)
	Negative	1 (25.0)	1 (11.1)	0.410 (1.000)
Herd size	<20	19 (39.6)	12 (41.4)
	20–50	16 (33.3)	8 (27.6)
	>50	13 (27.1)	9 (31.0)	0.305 (0.874)
IgM/IgG seropositivity in humans	Positive	11 (9.4)	24 (43.6)
	Negative	106 (90.6)	31 (56.4)	27.053 (<0.001)
RVFV PCR positivity in humans	Positive	2 (16.7)	5 (20.8)
	Negative	10 (83.3)	19 (79.2)	0.089 (1.000)
Sex	Male	17 (34.0)	12 (41.4)
	Female	33 (66.0)	17 (58.6)	χ^2 = 0.430 (0.629)
Age	0–12  months	28 (56.0)	15 (51.7)
	>12 months	22(44.0)	14 (48.3)	χ^2 = 0.135 (0.216)

Figure 2. RVFV PCR positivity in humans, goats and mosquitoes and RVFV seropositivity in humans and goats

Figure 3. Hypothetical diagram to show the transmission and maintenance mechanisms for RVFV in the study area