Volume 27, Number 9—September 2021
Research
Risk Factors for Middle East Respiratory Syndrome Coronavirus Infection among Camel Populations, Southern Jordan, 2014–2018
, Matthew Gibson, Neeltje van Doremalen, Stephen Nash, Tanja Holloway, Michael Letko, Jacqueline M. Cardwell, Bilal Al Omari, Ahmad Al-Majali, Ehab Abu-Basha, Punam Mangtani, Vincent J. Munster, and Javier Guitian
Table 4
Multivariate associations between potential risk factors and Middle East respiratory syndrome coronavirus seropositivity in camel populations, southern Jordan, October 2017–October 2018
| Variable* |
A priori adjusted OR (95% CI)† |
p value |
Fully adjusted OR (95% CI)‡ |
p value |
| Age, per y§ |
1.60 (1.35—1.99) |
<0.01 |
1.60 (1.34—1.92) |
<0.01 |
| Camels borrowed for breeding purposes |
4.46 (1.29—21.68) |
0.03 |
5.07 (1.37—18.75) |
0.02 |
| Water source¶ | ||||
| Open ad lib | Referent | 0.07 | Referent | 0.05 |
| Household only | 3.17 (0.44—25.78) | 3.33 (0.51—21.71) | ||
| Trough only |
7.93 (1.41—65.04) |
9.48 (1.54—58.24) |
||
| Region | ||||
| Ma’an |
3.28 (0.92—14.94) |
0.08 |
3.83 (1.01—14.51) |
0.05 |
| Herd size | ||||
| Increasing individual camel nos. |
1.02 (1.00—1.05) |
0.05 |
1.00 (1.00—1.05) |
0.10 |
| Sex§ | ||||
| F |
1.70 (0.59—4.88) |
0.32 |
1.38 (0.48—3.97) |
0.54 |
| No. camel herds within a 15-min drive | ||||
| >20 |
3.33 (0.77—17.53) |
0.11 |
2.40 (0.53—10.84) |
0.25 |
| Herd is kept together as single group throughout the year |
2.24 (0.61. 9.85) |
0.23 |
– |
– |
| Herd has contact with other local herds |
2.34 (0.65—9.85) |
0.19 |
– |
– |
| Camel is a racing camel§ |
0.73 (0.13—4.33) |
0.72 |
– |
– |
| Camels are lent for breeding purposes |
2.39 (0.66—10.70) |
0.19 |
– |
– |
| Closed herd# | 0.07 (0.01—0.43) | 0.01 | 0.08 (0.01—0.55) | 0.02 |
*Variables reference the 1-year period before sampling, with the exception of herd size, camel is a racing camel, and a priori variables: age, sex, and region. Because of the potential influence of maternal immunity, camels <6 m of age have been excluded. †Adjusted for a priori variables: age, sex, and region. ‡2017–2018 study was adjusted for a priori variables and number of camels nearby (within a 15 min drive), herd is kept as a single group throughout the year, herd has contact with other local herds, and camel is a racing camel. §Individual camel–level variables (all other variables being herd-level). ¶Open ad lib indicates irrigation reservoir or spring water sources were used; household only indicates water source was not shared between household and herd; trough only indicates only tanker, tap, or well sources were used. #Closed herd indicates herd owners answered no to all of the following variables: borrowing, lending, purchasing, racing, and contact with local or distant herds (2017–2018 study only, missing data 2014–2015). Because of collinearity with constituent variables, the variable closed herd was included in a separate multivariate model from camels are borrowed for breeding purposes and camels are lent for breeding purposes. In this model, all variables listed continued to demonstrate significant association (p<0.05) with Middle East respiratory syndrome coronavirus seropositivity, with the exception of water source (p = 0.07).