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. 2021 Mar 11;11(3):784.
doi: 10.3390/ani11030784.

Worldwide Prevalence of Small Ruminant Lentiviruses in Sheep: A Systematic Review and Meta-Analysis

Ricardo de Miguel  1 , Marta Arrieta  1 , Ana Rodríguez-Largo  1 , Irache Echeverría  2 , Raúl Resendiz  1 , Estela Pérez  1 , Héctor Ruiz  1 , Marta Pérez  3   4 , Damián de Andrés  2 , Ramsés Reina  2 , Ignacio de Blas  1   4 , Lluís Luján  1   4
Affiliations

Worldwide Prevalence of Small Ruminant Lentiviruses in Sheep: A Systematic Review and Meta-Analysis

Ricardo de Miguel et al. Animals (Basel). .

Abstract

Small Ruminant Lentiviruses (SRLV) are highly prevalent retroviruses with significant genetic diversity and antigenic heterogeneity that cause a progressive wasting disease of sheep called Maedi-visna. This work provides a systematic review and meta-analysis of the last 40 years (1981-2020) of scientific publications on SRLV individual and flock prevalence. Fifty-eight publications and 314 studies were included. Most articles used a single diagnostic test to estimate prevalence (77.6%), whereas articles using three or more tests were scarce (6.9%). Serological tests are more frequently used than direct methods and ELISA has progressively replaced AGID over the last decades. SRLV infection in sheep is widespread across the world, with Europe showing the highest individual prevalence (40.9%) and being the geographical area in which most studies have been performed. Africa, Asia, and North America show values between 16.7% to 21.8% at the individual level. South and Central America show the lowest individual SRLV prevalence (1.7%). There was a strong positive correlation between individual and flock prevalence (ρ = 0.728; p ≤ 0.001). Despite the global importance of small ruminants, the coverage of knowledge on SRLV prevalence is patchy and inconsistent. There is a lack of a gold standard method and a defined sampling strategy among countries and continents.

Keywords: maedi-visna; meta-analysis; prevalence; seroprevalence; small ruminant lentiviruses.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure A1
Figure A1
1 Keywords in Web of Science. maedi: 1641; maedi prevalence: 196; maedi-visna: 161; maedi-visna prevalence: 161; maedi/visna: 161; SRLV: 40; SRLV prevalence: 40; small ruminant lentivirus: 39; small ruminant lentivirus prevalence: 39. 2 Keywords in Pubmed. maedi: 733; maedi prevalence: 156; maedi-visna: 709; maedi-visna prevalence: 152; maedi/visna: 709; SRLV: 189; SRLV prevalence: 73; small ruminant lentivirus: 328; small ruminant lentivirus prevalence: 91. 3 Keywords in Scopus. maedi: 1019; maedi prevalence: 189; maedi-visna: 578; maedi-visna prevalence: 150; maedi/visna: 968; SRLV: 281; SRLV prevalence: 85; small ruminant lentivirus: 326; small ruminant lentivirus prevalence: 119. 4 Other sources. Conference Proceedings: 9; Google Scholar: 19. 5 Eligibility criteria: Information on SRLV prevalence; abstract available in English; publication from 1981 to 2020, inclusive. 6 Exclusion criteria: Total number of sampled animals not detailed; study focused on diseased sheep.
Figure 1
Figure 1
Analysis of diagnostic tests: (a) number of diagnostic tests performed in each article; and (b) evolution of the diagnostic tests from 1981 to 2020.
Figure 2
Figure 2
Individual SRLV prevalence (%) in sheep per country. Data extracted from scientific literature published from 1981 to 2020 and detailed in Table 2. Inset: Higher magnification of Europe.
Figure 3
Figure 3
Flock prevalence (%) of SRLV in sheep by country. Data extracted from scientific literature published from 1981 to 2020 and detailed in Table 3. Inset: Higher magnification of Europe.
Figure 4
Figure 4
Correlation between individual and flock SRLV prevalence: dots are the data of each individual study (n = 118); the red line is the linear regression; and the blue area is the 95% confidence interval of the linear regression [11,21,25,26,28,29,31,33,35,36,37,38,41,42,45,47,48,49,51,52,54,57,58,59,61,62,63,64,65,66,67,69,71,72,73,74,75].
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