In veterinary medicine, the recommendation to use thoracic ultrasound is becoming more widespread, as also are studies on this topic. In a study using pigs as the animal model, thoracic ultrasound was found to be useful for managing pneumonia, especially of viral origin (Wolfram et al. 2020). In a study on dogs and cats, findings of ultrasound alterations were associated with a diagnosis of pneumonia. These alterations consisted of thickened or irregular pleura (p = 0.034), consolidation (p = 0.032) and absence of nodular lesion or mass (p < 0.001) (Lin et al. 2020).
Abdominal ultrasound examinations on non-human primates, both for morphological and for hemodynamic evaluation, have already been well described in previous studies, with the aims of either diagnosing diseases or making periodic evaluations, especially with regard to evaluation of the reproductive system (Wilkinson 2008; Van Diepen et al. 2012; Zambon et al. 2018; Pissinatti et al. 2019; Wang et al. 2022).
Although use of chest ultrasound examinations for diagnosing diseases among humans is increasing, there are still no studies on non-human primates yet. The present study was the first to explore this topic and correlate ultrasound findings with diagnoses. It is known that pulmonary ultrasound is able to identify physical alterations in superficial lung tissue that correlate with histopathological findings, which often cannot be identified on chest x-rays (Soldati et al, 2020). In humans, chest ultrasound examinations have been found to have accuracy similar to that of tomography and to surpass that of chest x-rays, in patients with acute respiratory failure (Tierney et al. 2019). Moreover, this result was found to be the same as observed among children with pulmonary tuberculosis (Heuvelings et al. 2019).
Among humans with pneumonia due to SARS-CoV-2, predominance of B-lines was seen to be the main ultrasound finding, followed by the presence of lobar consolidation (Kong et al. 2021). This differed from the most common alterations seen on thoracic ultrasound examinations on the marmosets, which was the presence of lobar consolidation.
In the era of SARS-CoV-2, several studies have emerged related to the use of pulmonary ultrasound in cases of pneumonia, in addition some pictures demonstrated the sensitivity of ultrasound examination superior to chest X-ray (Staub et al. 2019; Kameda et al. 2021). These studies corroborate a study by Musolino et al. (2020) in pediatric patients with SARS-CoV-2, with symptomatic symptoms, in which pulmonary involvement was observed in all individuals evaluated, with the presence of vertical artifacts, consolidations or pleural irregularities. Therefore, pulmonary ultrasonography has gained prominence because of its ease of execution at the bedside and the clarifications about the condition of pulmonary parenchyma that it provides.
In a study on newborn humans with inflammatory bronchial disease, single or multiple consolidations of variable size, with diameters smaller than 1 cm, were observed in subpleural or pleural locations. Changes to pleural integrity and presence of variable quantities of B-lines were also detected (La Regina et al. 2021). No ultrasound evaluations on newborn non-human primates have ever been conducted, but in the present study it was observed that the mean age of the animals with consolidations was 3.9 years, i.e. relatively young animals, except for the 15-year-old animal that died (case 2), which was already an elderly individual (Fig. 5).
In a study on human patients without any history of inflammatory or infectious disease who underwent mechanical ventilation, sequenced pulmonary ultrasound was performed to evaluate the accuracy of the method for diagnosing pulmonary consolidations. The characteristics acquired through mechanical ventilation procedure were the following: areas of homogeneous appearance with absence or only slight presence of bronchograms; bronchograms with pleural effusion; bronchograms of heterogeneous appearance with the presence of dynamic aeration; bronchograms of heterogeneous appearance with static air bronchograms; and bronchograms of heterogeneous appearance with fluid bronchograms. Sensitivity of 100% and specificity of 60% was found in cases of consolidations with dynamic or static aeration (Berlet et al. 2015). These results demonstrate the importance of evaluation of non-human primates by means of ultrasonography, especially when these animals are in captivity and in contact with humans.
A meta-analysis conducted by Staub et al. (2018) showed that presence of consolidations may form useful confirmatory evidence for pneumonia, but that may not be the best diagnostic sign for ruling out this disease. In the present study, two patients with consolidations seen on ultrasound examination presented confirmation of pneumonia in postmortem examinations.
The histological similarities of the respiratory tract between humans and non-human primates demonstrate that the same pathophysiological processes occur during respiratory diseases (Lemaitre et al. 2021). Nonetheless. even though many studies have used non-human primates as models, such as for monitoring immune responses and pharmacological tests and even for infectious disease research (Walker et al. 2019; Hobbs and Reid 2021; Roubidoux and Schultz-Cherry 2021), the use of thoracic ultrasound for investigating respiratory diseases in these animals is not a subject that has been much addressed so far. Thus, the present study demonstrates the use of pulmonary ultrasound examination as a tool for diagnosing respiratory diseases, often in individuals that are still asymptomatic or that have nonspecific signs. Thus, this examination should be included as an instrument within health screening for these species and can contribute to early diagnosis, thus collaborating with their conservation.
Studies on non-human primates with SARS-CoV-2 infection have explored radiography and chest tomography as diagnostic and patient monitoring methods. However, ultrasound was not addressed as a method. Monitoring based on tomography as an investigative method can hinder early diagnosis, since this is an examination that requires general anesthesia for these animals and has a high cost (Maaskant et al. 2021; Stammes et al. 2022).
Ultrasound examination presents limitations regarding the device, probe and operator. Nonetheless, pulmonary ultrasound is more sensitive because it is able to identify small alterations that are not detectable on thoracic radiographic examination (Staub et al 2018; Hansell et al. 2021; Pérez 2021).