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Abortion in Alpaca and seroprevalence to Leptospira sp. in a herd in Treviso, Italy
Cornaggia, M., Palazzolo, L...
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Objective
Leptospirosis is a zoonosis affecting all mammals sustained by Leptospira sp.
Leptospira is worldwide distributed due to its persistence in humid environments and, to many asymptomatic carriers, spreading the pathogen for longtime through urines.
Several studies conducted in South America on new world camelids revealed a widespread seroprevalence to Leptospira sp. rising from 6,5 to 89,6% with various serovars positivity and different antibody titers (Rosadio, 2015).
Alpacas seem to not develop any clinical signs of leptospirosis but only some reproductive disorders such as abortion, infertility, and stillbirth (Tibary, 2006).
Materials and methods
In July 2021, a 9-month-old alpaca’s abortion belonged to an educational farm was delivered to the Diagnostic Service of IZSVe, Treviso, Italy for diagnostic purposes.
Placenta, liver, kidney and lung samples were processed as routine histological investigation.
Major abortion pathogens (Bovine Viral Diarrhea Virus; Chlamydia sp., Coxiella burnetii, Neospora caninum, Schmallenberg virus) were investigated through molecular methods
Investigations into bacteria were carried out on Campylobacter sp., Salmonella sp., and Listeria sp., and the content of abomasum was cultivated in standard bacteriological media.
Leptospira sp. was suspected as a cause of abortion. A real-time PCR (rPCR) was conducted on DNA extracted from lung, kidney, and spleen following the protocol previously described (Smythe, 2002).
Urines and blood sera of all animals in the herd (3 llamas; 25 alpacas) were collected monthly from the beginning of the outbreak (July, August and September).
Frozen sera collected on December 2020 (before the event of abortion) for other diagnostic purposes were also analyzed to compare the results obtained in July 2021.
Antibody titers were established by means of microagglutination test (MAT; OIE, 2021) while urine samples were analyzed in rPCR.
Results
The carcass was partially mummified and a diffuse hemorrhagic infiltration in organs and subcutis was recorded. Histologically, a mild degree of autolysis was observed. Lesions were characterized by hemorrhagic infiltration in organs. A necrotic placentitis occurred. Molecular and microbiological investigations gave negative results, except for rPCR against Leptospira sp. that resulted mild positive in the kidney of the aborted fetus. The weak Ct recorded in rPCR did not permit the sequencing of the amplicon.
The mother of the aborted fetus was tested for Leptospira sp. antibodies resulting negative before and after the outbreak. The serological study conducted to detect specific antibodies against a panel of 9 pathogenic serovars (Grippotyphosa; Copenagheni; Icterohaemorrhagiae; Pomona; Canicola, Tarassovi, Bratislava, Ballum, Hardjo) revealed a seroprevalence of 21,4%, 10,7%, 53,6% and, 28,6% to one or more serovars at December, July, August and September, respectively. The antibody titers varied from 1:100 to 1:6400; males showed a higher seroprevalence (p 0,0219) and a higher median of 1:200 titer values.
The most frequent serovar detected was Icterohaemorrhagiae; followed by Copenagheni, Grippotyphosa and Pomona. No symptoms were recorded at any times, nor was observed molecular positivity on urine.
Conclusions
Our work confirmed a probable pathogenic role of Leptospira sp. in new world camelids in Italy, as suggested by other authors in Europe (Rüfli, 2011).
Even if the rPCR on the aborted fetus gave a weak positivity and no bacterial DNA was detected in urine samples, serological investigations allowed us to confirm the Leptospira infection within the herd.
In absence of a clear seroconversion, it has been impossible to date the beginning of the outbreak. Due to the high persistent titers in the same subjects, probably the abortion represented its final event.
In a public health vision, to limit the zoonotic risk, a parenteral antimicrobial treatment with doxycycline for at least 2 weeks was encouraged by the Public Veterinary Service in combination with the official detention of the animals until a sink in the antibody titers.
Male alpacas showed higher seroprevalence and a higher median of antibody titers with respect to females, included the one who aborted. In cows, it is known that chronically infected subjects can remain seronegative, while very few studies were conducted in bulls.
Although urine collection in alpacas can be challenging, rPCR performed on this matrix is highly recommended to ensure the diagnosis. Authors intend to emphasize the complexity of the diagnosis of leptospirosis and the need to combine multiple diagnostic tools for a proper epidemiological investigation to create management protocols that mitigate the zoonotic risk.
Keywords: Alpaca leptospirosis, Alpaca abortion, Leptospira sp.
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