Seroprevalence of Bluetongue Virus in small ruminants in Balochistan province,Pakistan

Bluetongue (BT ), caused by bluetongue virus (BTV ), is a vector‐borne disease of small ruminants that has the potential to spread across international borders. Despite large populations of susceptible animals and borders with BTV endemic countries, little is known of the disease burden and prevalent serotypes in the province of Balochistan in Pakistan. We conducted a cross‐sectional study to determine seroconversion and prevalent serotypes in selected districts of the province using a competitive enzyme‐linked immunosorbent assay (cELISA ) and real‐time polymerase chain reaction (RT –PCR ). Sera (n  = 876) were collected from clinically healthy sheep and goats originating from the districts of Quetta (n  = 300), Mastung (n  = 201), Killa Saifullah (n  = 75) and Kech (n  = 300). None of the study herds (n  = 97) were seronegative for BTV , and at the individual level, the overall prevalence of BTV seroconversion was 47.26% (n  = 414/876, 95% CI  = 43.92%–50.63%). A higher percentage of goats (50.87%, 95% CI  = 45.99%–55.73%) were seropositive for anti‐VP 7 immunoglobulins (IgG) than sheep (44.21%, 95% CI  = 39.81%–48.70%). Odds ratios of seroconversion for goats were associated with breed type (χ² = 16.84, p  =  .01), parity (χ² = 23.66, p  =  .00) and presence of vector (χ² = 2.63, p  =  .10), whereas for sheep, it was associated with breed type (χ² = 13.80, p  =  .01) and parity (χ² = 53.40, p  =  .00). Serotype 8 was the most prevalent (26.82%, 95% CI  = 14.75%–43.21%) followed by an equal prevalence of serotypes 2 and 9 (7.31%, 95% CI  = 1.91%–21.01%). To the best of our knowledge, this is the first study conducted in Balochistan province and the results indicate that there is a necessity to initiate intervention strategies to control BT disease burden not only in this region of Pakistan but also in adjacent areas of the neighbouring countries, Iran and Afghanistan.     

Phylogenetic Characterization Genome Segment 2 of Bluetongue Virus Strains Belonging to Serotypes 5, 7 and 24 Isolated for the First Time in China During 2012 to 2014

Bluetongue is endemic in China, and Bluetongue virus (BTV) strains belonging to eight different serotypes (BTV‐1, BTV‐2, BTV‐3, BTV‐4, BTV‐9, BTV‐12, BTV‐15 and BTV‐16) had been isolated between 1996 and 1997. However, there has been a long pause in investigating the epidemiology of BTV infection since then. During 2012–2014, eight BTV strains belonging to serotypes 5, 7 and 24 were isolated for the first time in Yunnan and Guangdong provinces from the blood of sentinel animals. Phylogenetic analyses of genome segment 2 of these Chinese BTV strains grouped them into nucleotypes E, F and A, respectively, along with the reference strains of the same serotype. For each serotype, Chinese strains cluster together closely to form a China's sublineage. In addition, these strains were most closely related to strains from Africa, indicating that they may share a recent common ancestry with African strains. To our knowledge, this is the first time that BTV‐5, BTV‐7 and BTV‐24 strains have been isolated in South‐East Asia. These data will be beneficial for understanding the BTV epidemiology and improving diagnostic assays and control measures against bluetongue in China and its neighbouring countries in the Asia–Pacific region.     

Bluetongue Virus in Lebanon

Since 2000, several incursions of bluetongue virus (BTV) occurred in the Mediterranean Basin involving European and surrounding Countries. The Middle East represents one of the most important gateways for the access of BTV in Europe. Limited data on the BTV situation in this area are available. In this perspective, an epidemiological survey on the presence of BTV in Lebanon was conducted. Of the 181 serum samples tested, 97 (mean = 53.6%; 95% CI: 46.3–60.7) resulted positive when tested for the presence of BTV antibodies by c‐ELISA, of these 42 (mean = 42%; 95% CI: 32.8–51.8) serum samples were from sheep and 55 (mean = 67.9%; 95% CI: 57.1–77.1) serum samples were from goats. Fourteen blood samples (14/110; mean = 12.7%; 95% CI: 7.8–20.3), 6 (6/66; mean = 9.1%; 95% CI: 4.4–18.5) from sheep and 8 (8/44; mean = 18.2%; 95% CI: 9.6–32.0) from goats, were positive by qRT‐PCR. The results with serum‐neutralization assay and typing performed by RT‐PCR confirmed that six BTV serotypes are currently circulating in Lebanon, and these serotypes are as follows: 1, 4, 6, 8, 16 and 24. This study is the first report that confirms the presence and circulation of BTV in Lebanon.     

Evaluation of an IGM‐specific ELISA for early detection of bluetongue virus infections in domestic ruminants sera

Competitive‐ELISA (c‐ELISA) is the most widely used serological test for the detection of Bluetongue virus (BTV) viral protein 7 (VP7) antibodies (Ab). However, these BTV c‐ELISAs cannot to distinguish between IgG and IgM. IgM Ab are generated shortly after the primary immune response against an infectious agent, indicating a recent infection or exposure to antigens, such as after vaccination. Because the BTV genome or anti‐VP7 Ab can be detected in ruminant blood months after infection, BTV diagnostic tools cannot discriminate between recent and old infections. In this study, we evaluated an IgM‐capture ELISA prototype to detect ruminant anti‐BTV VP7 IgM on 1,650 serum samples from cattle, sheep, or goats. Animals were BTV‐naive, infected, or/and vaccinated with BTV‐1, ‐2, ‐4, ‐8, ‐9, ‐16, or ‐27, and we also included 30 sera from cattle infected with the Epizootic haemorrhagic disease virus (EHDV) serotype 6. Results demonstrated that this ELISA kit is specific and can detect the presence of IgM with satisfactory diagnostic specificity and sensitivity from 1 to 5 weeks after BTV infection in domestic ruminants (for goats and cattle; for sheep, at least up to 24 days). The peak of anti‐VP7 IgM was reached when the level of infectious viruses and BTV RNA in blood were the highest. The possibility of detecting BTV‐RNA in IgM‐positive sera allows the amplification and sequencing of the partial RNA segment 2 (encoding the serotype specific to VP2) to determine the causative BTV serotype/strain. Therefore, BTV IgM ELISA can detect the introduction of BTV (or EHDV) in an area with BTV‐seropositive domestic animals regardless of their serological BTV status. This approach may also be of particular interest for retrospective epidemiological studies on frozen serum samples.     

The serologic investigation and viral isolation of bluetongue virus in Shangri‐La in Southwest China

Bluetongue is an arthropod‐borne viral disease of ruminants caused by bluetongue virus (BTV). In China, BTV is relatively common in Yunnan Province with the exception of northern regions around Shangri‐La, where the average altitude is approximately 3,450 metres. Recently, the seroprevalence of BTV has been measured in yaks in Shangri‐La; therefore, this study investigated BTV infections in this area. The serological investigation in five villages in Shangri‐La showed that there were sporadic BTV infections in yaks (20 of 507 positive) during 2014 to 2017, while the seroprevalence of BTV at three goat farms in a nearby river valley was 35%–65% in 2017. Subsequently, 20 sentinel goats were kept on two separate farms in the river valley and monitored for seroconversion between May and September of 2017. Five of the sentinel animals were tested positive for antibodies to BTV by C‐ELISA during the study period, and 13 BTV isolates were isolated from ten sentinel animals. All isolates were identified as the same serotype, and the complete nucleotide sequence of one was determined. The genomic sequences showed that the isolated BTV strain belonged to serotype 21 and had approximately 99.8%–100% homology with three Indonesian BTV‐21 strains (D151, RIVS‐66 and RIVS‐60) between their coding sequences (CDSs) except for Seg4 (99.5%). Besides, our data suggested that this BTV‐21 strain might have also infected some local yaks and sheep.     

Factors Affecting Seroconversion Rates in Cattle Vaccinated with Two Commercial Inactivated BTV‐8 Vaccines Under Field Conditions

The immunogenicity of two inactivated bluetongue virus serotype 8 (BTV‐8) vaccines was evaluated in 880 cattle under field conditions. The effect of selected factors on vaccine performance was also analysed at the herd and animal levels (vaccine, herd size and production, age, sex, time interval between vaccination and blood sampling and veterinary training). The immunogenicity elicited by vaccination with the two vaccines was monitored with the aid of a competitive enzyme‐linked immunosorbent assay (c‐ELISA) and serum neutralization test (SNT). To investigate whether the selected factors influenced seroconversion at the herd and animal levels, a multilevel logistic regression model developed in a mixed model was applied. Of the 880 cattle vaccinated, 76.0% yielded BTV c‐ELISA antibodies, whereas only 25.0% seroconverted based on SNT. Type of vaccine (odds ratio [OR] 4.5; 95% confidence interval [CI], 2.2–9.0 for SNT and OR 3.5; 95% CI, 2.1–5.9 for c‐ELISA), veterinary training in vaccine administration (OR 8.1; 95% CI, 4.7–14.1 for SNT and OR 2.4; 95% CI, 1.3–4.2 for c‐ELISA), animal age (OR 1.4; 95% CI, 1.1–1.8 for SNT and OR 1.7; 95% CI, 1.4–2.1 for c‐ELISA) and days between first vaccine administration and blood collection (OR 1.9; 95% CI, 1.1–3.1 for SNT and OR 2.6; 95% CI, 1.7–3.8 for c‐ELISA) were the major factors affecting vaccine performance under field conditions. This is the first study to use multilevel logistic regression in the evaluation of selected risk factors affecting BTV‐8 vaccine performance in cattle.     

Western Bluetongue virus serotype 3 in Sardinia,diagnosis and characterization

Over the last 20 years, Italy has experienced multiple incursions of different serotypes of Bluetongue virus (BTV), a Culicoides‐borne arbovirus, the causative agent of bluetongue (BT), a major disease of ruminants. The majority of these incursions originated from Northern Africa, likely because of wind‐blown dissemination of infected midges. Here, we report the first identification of BTV‐3 in Sardinia, Italy. BTV‐3 circulation was evidenced in sentinel animals located in the province of Sud Sardegna on September 19, 2018. Prototype strain BTV‐3 SAR2018 was isolated on cell culture. BTV‐3 SAR2018 sequence and partial sequences obtained by next‐generation sequencing from nucleic acids purified from the isolate and blood samples, respectively, were demonstrated to be almost identical (99–100% of nucleotide identity) to BTV‐3 TUN2016 identified in Tunisia in 2016 and 2017, a scenario already observed in past incursions of other BTV serotypes originating from Northern Africa.     

Emergence of a Novel Bluetongue Virus Serotype,China 2014

One hundred and twenty‐six blood samples were collected from healthy sheep and goats in Xinjiang, China, during July 2014. Seventy‐three samples (57.93%) were bluetongue virus (BTV) serology‐positive, and 39 samples (30.95%) were BTV NS1 gene‐positive. BTV strain XJ1407 was isolated from the blood of BTV NS1 gene‐positive animals and sequenced. Analysis of its genome sequence suggests that XJ1407 is a novel BTV serotype.     

Bluetongue Virus Serotype 8‐Associated Congenital Hydranencephaly in Calves

Hydranencephaly, the almost complete absence of the cerebral parenchyma, induced by infection with modified live bluetongue virus (BTV) crossing the placenta has previously been reported in sheep and rarely in cattle in the USA and in South Africa. The current study describes 29 cases of hydranencephaly in bovine foetuses and ‘dummy’ calves up to 3 months of age in Belgium associated with natural BTV serotype 8 infection very early in gestation. Histological examination of the remaining cerebral parenchyma showed moderate to severe atrophy of the neural tissue. The lesions observed support the hypothesis of BTV‐induced destruction of precursor cells. However, in several calves a slight infiltration of the walls of venules and arterioles with T lymphocytes (vasculitis) was observed as well, which seems to be responsible for at least some of the lesions. Bluetongue viral RNA was detected in 15 animals using a BTV‐specific real‐time RT‐PCR with a much higher success rate in brain tissues compared with blood and spleen samples. Virus isolation in embryonated eggs was unsuccessful. In conclusion, hydranencephaly in calves can be associated with natural wild‐type BTV‐8 intra‐uterine infection.     

Bluetongue virus serotype 27: Experimental infection of goats,sheep and cattle with three BTV‐27 variants reveal atypical characteristics and likely direct contact transmission BTV‐27 between goats

Bluetongue virus (BTV) hitherto consisted of 26 recognized serotypes, of which all except BTV‐26 are primarily transmitted by certain species of Culicoides biting midges. Three variants of an additional 27th bluetongue virus serotype (BTV‐27v01‐v03) were recently detected in asymptomatic goats in Corsica, France, 2014–2015. Molecular characterization revealed genetic differences between the three variants. Therefore, in vivo characteristics were investigated by experimental infection of a total of 15 goats, 11 sheep and 4 cattle with any one of the three variants in separated animal trials. In goat trials, BTV‐naïve animals of the same species were kept in a facility where direct contact was unhindered. Of the 15 inoculated goats, 13 and 14 animals were found positive for BTV‐RNA and antibodies (Ab), respectively, until the end of the experiments. Surprisingly, BTV‐Ab levels as measured with ELISA and neutralization test (SNT) were remarkably low in all seropositive goats. Virus isolation from whole‐blood was possible at the peak of viremia until 49 dpi. Moreover, detection of BTV‐27v02‐RNA and Ab in one contact goat indicated that—similar to BTV‐26—at least one of three BTV‐27 variants may be transmitted by contact between goats. In the field, BTV‐27 RNA can be detected up to 6 months in the whole‐blood of BTV‐27‐infected Corsican goats. In contrast, BTV RNA was not detected in the blood of cattle or sheep. In addition, BTV‐27 Abs were not detected in cattle and only a transient increase in Ab levels was observed in some sheep. None of the 30 animals showed obvious BT‐like clinical signs. In summary, the phenotypes observed for BTV‐27v01‐v03 phenotypes correspond to a mixture of characteristics known for BTV‐25 and 26.     

Evidence of reduced viremia,pathogenicity and vector competence in a re‐emerging European strain of bluetongue virus serotype 8 in sheep

The outbreak of bluetongue virus (BTV) serotype 8 (BTV‐8) during 2006–2009 in Europe was the most costly epidemic of the virus in recorded history. In 2015, a BTV‐8 strain re‐emerged in France which has continued to circulate since then. To examine anecdotal reports of reduced pathogenicity and transmission efficiency, we investigated the infection kinetics of a 2007 UK BTV‐8 strain alongside the re‐emerging BTV‐8 strain isolated from France in 2017. Two groups of eight BTV‐naïve British mule sheep were inoculated with 5.75 log₁₀TCID₅₀/ml of either BTV‐8 strain. BTV RNA was detected by 2 dpi in both groups with peak viraemia occurring between 5–9 dpi. A significantly greater amount of BTV RNA was detected in sheep infected with the 2007 strain (6.0–8.8 log₁₀ genome copies/ml) than the re‐emerging BTV‐8 strain (2.9–7.9 log₁₀ genome copies/ml). All infected sheep developed BTV‐specific antibodies by 9 dpi. BTV was isolated from 2 dpi to 12 dpi for 2007 BTV‐8‐inoculated sheep and from 5 to 10 dpi for sheep inoculated with the remerging BTV‐8. In Culicoides sonorensis feeding on the sheep over the period 7–12 dpi, vector competence was significantly higher for the 2007 strain than the re‐emerging strain. Both the proportion of animals showing moderate (as opposed to mild or no) clinical disease (6/8 vs. 1/8) and the overall clinical scores (median 5.25 vs. 3) were significantly higher in sheep infected with the 2007 strain, compared to those infected with the re‐emerging strain. However, one sheep infected with the re‐emerging strain was euthanized at 16 dpi having developed severe lameness. This highlights the potential of the re‐emerging BTV‐8 to still cause illness in naïve ruminants with concurrent costs to the livestock industry.     

Re‐Emergence of Bluetongue Virus Serotype 8 in France, 2015

At the end of August 2015, a ram located in central France (department of Allier) showed clinical signs suggestive of BTV (Bluetongue virus) infection. However, none of the other animals located in the herd showed any signs of the Bluetongue disease. Laboratory analyses identified the virus as BTV serotype 8. The viro and sero prevalence intraherd were 2.4% and 8.6% in sheep and 18.3% and 42.9% in cattle, respectively. Phylogenetic studies showed that the sequences of this strain are closely related to another BTV‐8 strain that has circulated in France in 2006–2008. The origin of the outbreak is unclear but it may be assumed that the BTV‐8 has probably circulated at very low prevalence (possibly in livestock or wildlife) since its first emergence in 2007–2008.     

Dual Infection with Bluetongue Virus Serotypes and First‐Time Isolation of Serotype 5 in India

Bluetongue is endemic in India and has been reported from most Indian states. Of late, the clinical disease is most frequently seen in the states of Andhra Pradesh, Telangana (erstwhile Andhra Pradesh state), Tamil Nadu and Karnataka. Our analysis of diagnostic samples from bluetongue outbreaks during 2010–2011 from the state of Karnataka identified bluetongue virus (BTV) serotype 5 (BTV‐5) for the first time in India. One of the diagnostic samples (CH1) and subsequent virus isolate (IND2010/02) contained both BTV‐2 and BTV‐5. Segment 2 (seg‐2) sequence data (400 bp: nucleotides 2538–2921) for IND2010/02‐BTV5, showed 94.3% nucleotide identity to BTV‐5 from South Africa (Accession no. AJ585126), confirming the virus serotype and also indicating that Seg‐2 was derived from a Western topotype, which is in contrast to serotype 2, that belongs to an Eastern topotype. BTV‐5 has been recently reported from Africa, China, French islands and the Americas. Although the exact source of the Indian BTV‐5 isolate is still to be confirmed, recent identification of additional exotic serotypes in India is of real concern and might add to the severity of the disease seen in these outbreaks.     

Isolation of Bluetongue Virus Serotype 1 from Culicoides vector Captured in Livestock Farms and Sequence Analysis of the Viral Genome Segment‐2

Bluetongue virus serotype‐1 (BTV‐1) was isolated from Culicoides oxystoma vectors captured on livestock farms in two places of Gujarat, India. The viruses were isolated on BHK‐21 cells, which produced characteristic BTV‐related cytopathic effects between 24 and 48 h post‐infection. Virus antigen was demonstrated in infected cells at different passage by a BTV‐specific sandwich ELISA. Further, polyacrylamide gel electrophoresis and silver staining of viral genomic RNA revealed ten double‐stranded RNA segments characteristic of BTV. Serotype of the isolates was identified by virus neutralization and PCR coupled with sequencing. The isolates were designated as SKN‐7 and SKN‐8 and their genome segment‐2 (VP2) were sequenced. Phylogenetic analyses revealed very close relationship between them although they are not identical. SKN‐8 showed closer relationship with a recently isolated BTV‐1 from goat. Bluetongue virus was earlier isolated from Culicoides in adjacent state more than 20 years ago, although the serotype of the virus was not determined.     

Concurrent infection of Bluetongue and Peste‐des‐petits‐ruminants virus in small ruminants in Haryana State of India

Bluetongue (BT ) and peste‐des‐petits‐ruminants (PPR ) are major transboundary diseases of small ruminant, which are endemic in India. Testing of bluetongue virus (BTV ) and peste‐des‐petits‐ruminants virus (PPRV ) from recent outbreaks (2015–2016) in different regions of Haryana State of India revealed that 27.5% of the samples showed the presence of dual infection of BTV and PPRV . Analysis of Seg‐2 of BTV (the serotype‐determining protein) showed the presence of BTV ‐12w in several isolates. However, analysis of N gene fragment amplicons showed that viruses belong to lineage IV were most closely related to a pathogenic strain of PPRV from Delhi. This is the first report of co‐circulation of PPRV lineage IV and bluetongue virus serotype 12 in the state.     

Sequences of Genes Encoding Type‐Specific and Group‐Specific Antigens of an Indian Isolate of Bluetongue Virus Serotype 10 (BTV‐10) and Implications for their Origin

Bluetongue, a transboundary disease, is endemic in several tropical countries and is caused by bluetongue virus (BTV). The origin and movement of BTV can be predicted by comparing nucleotide sequences of its segmented RNA genome. Such analyses have been useful in evaluating the source of the virus responsible for recent incursion of BTV into previously unreported areas. Besides several serotypes, genetically related BTV strains circulate in each endemic area, but such clusters of strains have been reported to be distinct from one geographical region to another. We obtained partial or complete sequences of the open reading frames encoded by VP2, VP6, VP7, NS1 and NS2 genes of a BTV‐10 isolate of India and compared them with other BTV‐10 sequences available in public database. Sequences of all the five genes showed >99% identity to BTV‐10 prototype, vaccine strain and vaccine‐like virus isolates from the USA. Our results suggest that Indian BTV‐10 virus analysed in this study possibly originated from the United States.     

Transplacental Infection and Apparently Immunotolerance Induced by a Wild‐type Bluetongue Virus Serotype 8 Natural Infection

Until recently, bluetongue (BT) virus (BTV) serotypes reportedly causing transplacental infections were all ascribed to the use of modified live virus strains. During the 2007 BT epidemic in Belgium, a significant increase in the incidence of abortions was reported. A study including 1348 foetuses, newborns and young animals with or without suspicion of BTV infection, was conducted to investigate the occurrence of natural transplacental infection caused by wild‐type BTV‐8 and to check the immunocompetence of newborns. BTV RNA was present in 41% and 18.5% of aborted foetuses from dams with or without suspected BTV involvement during pregnancy, respectively. The results of dam/calf pairs sampled before colustrum uptake provide evidence of almost 10% transplacental BTV infection in newborns. Apparently immunotolerant calves were found at a level of 2.4%. The current study concludes that the combined serological and real‐time PCR (RT‐qPCR) result of pregnant dams gives no indication of the infection status of the offspring except in the case of a double negative result. In a group of 109 calves with clinical suspicion of BT, born during the vector‐free period, 11% were found to be RT‐qPCR positive. The true prevalence was estimated to be 2.3%, indicating the extent of transplacental infection in a group of 733 calves of one to 4 months of age without BT suspicion. Moreover, virus isolation was successful for two newborn calves, emphasizing the need for restricting trade to BT‐free regions of pregnant dams possibly infected during gestation, even if they are BTV RT‐qPCR negative.     

Spatiotemporal monitoring of selected pathogens in Iberian ibex (Capra pyrenaica)

An epidemiological surveillance programme was carried out to assess exposure and spatiotemporal patterns of selected pathogens (Brucella spp., Mycobacterium avium subsp. paratuberculosis (MAP), Mycoplasma agalactiae, Pestivirus and bluetongue virus (BTV)) in Iberian ibex (Capra pyrenaica) from Andalusia (southern Spain), the region with the largest population of this species. A total of 602 animals in five distribution areas were sampled during 2010–2012 (P1) and 2013–2015 (P2). The Rose Bengal test (RBT) and complement fixation test (CFT) were used in parallel to detect anti‐Brucella spp. antibodies. Commercial ELISAs were used to test for antibodies against the other selected pathogens. Sera positive for BTV and Pestivirus by ELISA were tested by serum neutralization test (SNT) to identify circulating serotypes/genotypes. The overall seroprevalences were as follows: 0.4% for Brucella spp. (2/549; CI 95%: 0.1–1.3) (14/555 positive by RBT; 2/564 by CFT), 0.5% for MAP (3/564; CI 95%: 0.1–1.5), 5.7% for M. agalactiae (30/529; CI 95%: 3.9–8.0), 11.1% for Pestivirus (58/525; CI 95%: 8.5–14.1) and 3.3% for BTV (18/538; CI 95%: 2.0–5.2). Significantly higher seropositivity to both M. agalactiae and BTV was observed in P1 compared with P2. Spatiotemporal clusters of high seroprevalence were also found for M. agalactiae in four of the five sampling areas in 2010, and for BTV in one of five areas in 2012. Specific antibodies against BTV‐4, BDV‐4 and BVDV‐1 were confirmed by SNT. Our results indicate that the Iberian ibex may be considered spillover hosts of Brucella spp. and MAP rather than true reservoirs. The prevalence of antibodies against M. agalactiae and BTV suggests spatiotemporal variation in the circulation of these pathogens, while Pestivirus has a moderately endemic circulation in Iberian ibex populations. Our study highlights the importance of long‐term surveillance for a better understanding of the spatiotemporal distribution of shared infectious diseases and providing valuable information to improve control measures at the wildlife–livestock interface.     

Sensitivity,specificity and predictive probability values of serum agglutination test titres for the diagnosis of Salmonella Dublin culture‐positive bovine abortion and stillbirth

The objective of this study was to determine the diagnostic value of maternal serology for the diagnosis of Salmonella Dublin bovine abortion and stillbirth. A retrospective, unmatched, case–control study was carried out using twenty year's data (1989–2009) from bovine foetal submissions to an Irish government veterinary laboratory. Cases (n  = 214) were defined as submissions with a S . Dublin culture‐positive foetus from a S . Dublin unvaccinated dam where results of maternal S . Dublin serology were available. Controls (n  = 415) were defined as submissions where an alternative diagnosis other than S . Dublin was made in a foetus from an S . Dublin unvaccinated dam where the results of maternal S . Dublin serology were available. A logistic regression model was fitted to the data: the dichotomous dependent variable was the S . Dublin foetal culture result, and the independent variables were the maternal serum agglutination test (SAT ) titre results. Salmonella serology correctly classified 87% of S . Dublin culture‐positive foetuses at a predicted probability threshold of 0.44 (cut‐off at which sensitivity and specificity are at a maximum, J  = 0.67). The sensitivity of the SAT at the same threshold was 73.8% (95% CI : 67.4%–79.5%), and the specificity was 93.2% (95% CI : 90.3%–95.4%). The positive and negative predictive values were 84.9% (95% CI : 79.3%–88.6%) and 87.3% (95% CI : 83.5%–91.3%), respectively. This study illustrates that the use of predicted probability values, rather than the traditional arbitrary breakpoints of negative, inconclusive and positive, increases the diagnostic value of the maternal SAT . Veterinary laboratory diagnosticians and veterinary practitioners can recover from the test results, information previously categorized, particularly from those results declared to be inconclusive.